How Satellite Data Can Aid Archeology

For hundreds of years, maybe even thousands, humans have been digging holes, trying to unearth treasures of a bygone age. It is a messy affair, lots of shoveling and moving large amounts of dirt or sand. When it gets down to it small trowels may need to be used or even little brushes. How do we know where to dig? Well sometimes there are already existing structures, or the remnants of buildings. There could also be a building that has been there a long time. We just have to find hints that something interesting is under the ground. Archaeology can find things like pottery, tools and coins, but also parts of old structures. The problem is that more often than not these things are buried, else we would already know about them. In recent years archaeologists have used remote sensing methods to have a basic look underneath the ground before they dig it up. Basically the devices send a signal into the ground and see what gets reflected back. This can be very time consuming, moving equipment to a random field and spend all day setting up and getting reasonable measurements. Now with the increase of satellite technology there is a new way to look for new sites.

Inverted kite aerial photo of an excavation of a Roman site at Nesley near Tetbury in Gloucestershire. Taken on a kite line. Credit: Dr John Wells

The method of using satellite imagery, such as that found on Google Maps, is generally referred to as an aerial survey. Traditionally this was done using cameras attached to an airplane, balloon or UAV’s. People have also been known to use kites! These pictures can be useful to help map a large area, or a site that is particularly complex. Plus if they are taken fairly often then they can be used to document to progress and status of the dig. This angle of image can also help to detect things not obvious from the ground. Things like different coloured soil/sand, or locations of certain types/colours of flowers can hint at a buried structure or wall. When solid rocks develop under plants they tend to grow slower, so a wall may actually be fairly obvious if looked at over time. Certain plants such as ripening grain changes colour rapidly, and if anything slows it down then it is noticeable compared to the other grain. When looking at different times of day the shadows could show areas of a field that are slightly raised from its surrounding.

In this satellite image, the white arrows show a potential previously unknown buried pyramid and the black arrows other structures which have yet to be investigated. Credit: National Research Council, Italy.

With more and more Earth monitoring satellites going up all the time, companies like Planet Labs can now offer a satellite image of a specified part of land with updated images in the days and sometimes hours timescale. There have also been changes in the type of satellite going up, they are no longer just taking standard images. Modern technology allows the use of sensors seeing different wavelengths of light. The different bands of the electromagnetic spectrum can tell us different things about the thing you are looking at, and most of the spectrum, the human eye cannot see. Most of these satellites are designed to be used to look at weather conditions, specifically things like clouds and effect on the ground. Many modern weather satellites use microwave sensors to probe the ground. Much like microwave radar used to track airplanes, the satellites can send a signal towards the ground, and the signal that gets reflected back can say plenty about the surface. This is similar to the way ground penetrating radar works. SAR (Synthetic Aperture Radar) satellites are an example of this technology. There is also a good portion of satellites with Infrared spectrum sensors. This band is often giving data on aspects like temperature, showing how different sections of land are reacting to weather conditions can say plenty about what the ground is made of. There are also other methods to map the surface, such as LIDAR which is used in range finding applications, showing distances from the satellite to the ground.

Airborne laser-scanning technology, called LiDAR, provides a 3-D map of part of the Maya city at Caracol in Belize. LiDAR cuts through the jungle to reveal the hidden features beneath, a revolution in the study of ancient Maya landscapes. Credit: Courtesy Arlen Chase

Even though this is a fairly new technology for archaeology, there have been some significant uses of it. One of the most prominent uses have been to study the Maya civilization in ancient Mesoamerica. A particular area of interest is the Petén region of northern Guatemala. Very dense forest, and little to no modern settlements in the area make it difficult to study. Remote sensing has allowed scientists to study potential causeways and canals used by this early civilization. There have also been hints at cisterns and temples and buildings that they may have lived in. This allows for archaeologists to have a much better idea of where to look, without ever having to visit the jungle. In Peru, a group of Italian scientists have been getting results using satellite imagery. They have managed to get images of a buried settlement, including a pyramid in a riverbed. The North of Peru has also been known to be a haven for clandestine excavations. Satellite data has been useful to map and monitor archaeological looting. There have also been attempts to find lost cities such as Iram of the Lost Pillars in the Arabian Peninsula. The researchers found interesting information on old trade routes and uncovered a previously unknown settlement. There is also an award winning TED talk by Dr Sarah Parcak on using citizen science to search for sub-surface remains, Using normal people looking at satellite images they have prospectively found several significant sites in various parts of Egypt and the ancient Roman Empire.

A LiDAR image of the Caana complex at the heart of Caracol, at left, shows the tree canopy surrounding a 140-foot-tall building (in an aerial photo at right). The lasers also penetrate the jungle to reveal structures hidden by that overgrowth. Credit: Courtesy Arlen Chase.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or general history. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts.

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A Great Start to the Space Year

2018 was a great year for space, but it was barely a few days into 2019 and three amazing achievements in space have happened. We had new Horizons studying the furthest object studied in space, the Chinese space agency landing a rover on the far side of the Moon, and OSIRIS-REx mission reached bennu.

New Horizons

By far the biggest news in the space sector recently, New Horizons officially flew by object 2014 MU69, the outermost close encounter of any Solar System object. Launching in 2016, New Horizons was a mission designed to help us understand the worlds at the edge of our Solar System. The biggest part of the mission was in 2015 when it made the first reconnaissance of the dwarf planet Pluto, producing some amazing photos. After that it kept venturing out into the Kuiper Belt to study more mysterious objects. The spacecraft is helping us to understand the basic questions about the surface properties, interior makeup, geology and atmosphere of the bodies it passes. The exploration of the Kuiper belt is one of the big priorities in planetary science currently. New Horizons fits into this plan, by seeing how Pluto and its Moons “fit in” to the other objects in the Solar System. It has already aided in finding four previously unknown Moons of Pluto, and studied the known Moon Charon in much more detail.

New Horizons Artist
An artistic impression of what New Horizons looked like when it passed Pluto and Charon. Credit: NASA Goddard Media Studios.

New Horizons was designed, built and is operated by The John Hopkins University Applied Physics Laboratory in Laurel, Maryland. Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado is the principal investigator. It flew by the Kuiper belt object 2014 MU69 barely a few hours into the new year at 05:33 UTC on January 1st 2019. The flyby technically ends on January 9th, where it switches from 3-axis mode to spin mode. This is the beginning of the downlink phase which could run for around 18 months! This is because it is so far away, the frequency (and therefore the data rate) is much lower than if the spacecraft was close. The current extended mission is planned to last until April 30th, 2021. If still operational there may be a new extended mission, but it has very limited fuel at about 11kg. The craft could in theory visit another Kuiper Belt object. If it lasts until the mid 2030’s it will join Voyager 2 in the Heliosphere, but based on the RTG it may run out about then.

Ultima Thule
Image of 2014 MU69, taken 30 minutes before closest approach from a distance of 28,000 km (17,000 mi). Credit: NASA/John Hopkins Applied Physics Laboratory.

Chang-E4

On January 3rd 2019 at 02:26 UTC China’s Chang’e-4 spacecraft successfully landed on the far side of the Moon. The first ever soft landing on the far side of the Moon, up until this point we only has remotely sensed images. The target of the spacecraft was the Von Kármán crater, located within the South Pole-Aitken basin. This is where an ancient lunar impact may have exposed some of the Moon’s mantle. The plan is to study this region directly with the rover and the lander. It also allows for a close up look at the far side of the Moon, which could be a perfect place for science applications such as radio astronomy. As there is no direct line of sight to the far side of the Moon they need a relay satellite. The satellite that China launched is the Queqiao relay satellite, launched in May 2018.

An image of the rover similar to the Chang’e-3’s rover. Credit: CNSA.

OSIRIS-Rex

Coming into the new year, on December 31st OSIRIS-REx entered orbit around Bennu. The orbit is at around 1.75 km (just over a mile), and is the place it will be doing an extensive remote sensing campaign. 101955 Bennu, or 1999 RQ36, is a carbonaceous asteroid in the Apollo group. Discovered in 1999, it has a 1 in 2700 chance of impacting Earth between 2175 and 2199. The name Bennu references the Egyptian mythological bird associated with the sun, creation and rebirth. The OSIRIS-REx mission is a sample return mission to the asteroid Bennu. Its goal is to obtain a sample of at least 60g and then bring that sample back to Earth for scientific study. The aim is to help scientists to learn about the formation and evolution of Solar System in its initial stages of planet formation and the source of organic compounds that eventually lead to life. If the mission is successful on September 24th 2023 it will be the first US spacecraft to return samples from an asteroid.

Asteroid Bennu, imaged by the OSIRIS-REx probe (3 December 2018). Credit: NASA/ Goddard/ University of Arizona.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts this year! So all have a Happy New Year, and here’s to a great 2019 in space!

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The Space Missions of 2018

2018 has definitely been a big year for space, and space exploration. I have managed to capture a few of the great moments like the launch of InSight, JAXA landing rovers on an asteroid, and the launch of the Parker Probe. There have been a few others that are notable mentions, and that is the point of this post, to talk about some great launched missions, and others that have finished their jobs, purposely or forced.

Bepicolombo

The British built Bepicolombo launched in October 20th, to begin its 7 year journey to visit Mercury. Currently one of the least explored planets in the solar system, Bepicolombo intends to change that. When it arrives in late 2025 it will endure temperatures of over 350 °C, and be there for at least a year, possibly for twice that. It is made up of two spacecraft, the Mercury Planet Orbiter (MPO) lead by ESA, and the Mercury Magnetospheric Orbiter (MMO) lead by JAXA. The aim is to measure the composition, atmosphere and magnetosphere of Mercury to understand its history. This could lead to understanding more about how other planets such as Earth formed. BepiColombo is named after Professor Giuseppe (Bepi) Colombo (1920-1984) from the University of Padua, Italy. He made big leaps in understanding Mercury, and suggested to NASA how to use a gravity-assist swing-by of Venus to place Mariner 10 into a solar orbit of Mercury.

Bepicolombo artists impression
Artist’s impression of the BepiColombo spacecraft in cruise configuration. The Mercury Transfer Module is at the bottom. The Mercury Planetary Orbiter is in the middle. The Mercury Magnetospheric Orbiter sits inside the sunshield, visible at the top. Credit: ESA/ATG medialab

InSight

Back in May I posted about how an Atlas V had just lifted the Mars Insight lander. In late November the $814 million lander it reached its target of the Elysium Planitia region of Mars, landing safely. The aim is for it investigate how the processes that shaped all the inner rocky planets more than 4 billion years ago worked. It uses two seismometers (one of which built by RAL space in the UK) and a number of other instruments to study the crust, mantle and core of the red planet. It works by measuring how much the area shakes when asteroids hit the planet. Also measuring the heat flow and precision tracking it is getting a glimpse of Mars we have yet to see. The launch also allowed for two cubesats, MarCO-A and MarCO-B to be the first to be launched into deep space. The first test of miniaturised cubesat technology being used on another planet. This mission will be one to watch for the near future.

There’s a quiet beauty here. Looking forward to exploring my new home. #MarsLanding pic.twitter.com/mfClzsfJJr— NASA InSight (@NASAInSight) November 27, 2018

Kepler

A bit sadder news is the end of the Kepler space telescope after 9 years service. It has collected a huge amount of data in its lifetime, finding the night sky is filled with billions of hidden planets, more planets than stars. This may seem obvious but is not easy to prove. During its time the planet hunter has found evidence of more than 2,600 planets outside our solar system, and left hints at many more, paving the way for future planet hunters and getting good engineering data on what works and what doesn’t. Telescopes such as ARIEL which will launch in the net decade will have better design due to Kepler. The space telescope had been running low on fuel for months, and struggled to point the correct way. After the 4 year mission it continued to work a different mission named K2. In October it was officially declared dead, left in orbit as it may have been dangerous for it to enter the atmosphere.

The Kepler Space Telescope mission, by the numbers
The Kepler Space Telescope mission, by the numbers. Credit: NASA/Ames/Wendy Stenzel

Parker Solar Probe

Back in august I wrote about the classic Delta IV heavy launching with the Parker Solar Probe aboard. The aim is to get closer to the sun than previously possible. Over the next seven years the probe will make 24 close approaches to the sun, with the aim of eventually getting within 3.8 million miles of the surface. The previous record (that Parker has now broken) was 26.6 million miles, set in 1976. It will revolutionise our understanding of the sun, and how the changing conditions can affect the solar system. It will use Venus’ gravity to slowly get closer to the sun. As a reference, we are 93 million miles away from the sun. It will eventually fly through the sun’s outer atmosphere, known as the Corona for the first time, getting brand new, in situ measurements. The spacecraft has a 4.5 inch thick carbon composite shield to protect it from the heat and radiation. The temperatures will reach over 1300 C.

Parker Solar Probe in the Fairing
Parker Solar Probe in the Fairing, ready to be put on the rocket in the clean room. Credit: NASA/Johns Hopkins APL/Ed Whitman

TESS

Back in April I posted about the launch of the TESS exoplanet hunter by a Falcon 9. I have already talked about exoplanets and planet hunters, and this is a big part of that plan. TESS stands for Transiting Exoplanet Surveying Satellite, and it does what it says on the tin, it is surveying the sky for potential exoplanets. Basically it is looking for exoplanets that could harbour life. The expectation is that it will catalog thousands of planet candidates and vastly increase the known number of exoplanets. Approximately 300 are expected to be Earth-sized and super-Earth-sized exoplanets that can then use the future more complex telescopes such as JWST to look at in more detail. The satellite will look at the sky for two years by breaking it up into 26 sections, and looking at each one for 27 days at a time. Unlike Kepler and K2 TESS will be looking at brighter stars, meaning ground based observatories can corroborate the observations.

the TESS telescope
The TESS satellite before launch, the four cameras can be seen on the top of the spacecraft; Credit: NASA.

Dawn

In September I posted about the Dawn spacecraft and the rise of Ion Engines. With the loss of the Dawn mission around the same time as Kepler, they ran out of fuel within two days of each other. The 11 year Dawn mission racked up a few very important records. It is the first spacecraft to orbit two different celestial bodies, and the first to orbit any object in the main asteroid belt between Mars and Jupiter. It is also a record breaker for electric speed. Travelling over 25,700 mph. Visiting Ceres and Vesta, it found out some very important scientific data that tells us a huge amount about the formation of our solar system. With a large proportion of the meteorites hitting Earth coming from these two bodies, Dawn showed the difference between the potential dwarf planets. One of the early uses of ion engines, it also showed the potential of the efficient form of travel, and now many more satellites are using them.

Dawn prior to encapsulation at its launch pad on July 1, 2007. Credit: NASA/Amanda Diller

Mars Rovers

This is a mixed bag, we have already had great news about the InSight lander, with it recording sounds of Martian winds, the rovers also have big news this year. In June the Curiosity rover found Organic matter in the Martian soil. The samples, taken from 3 billion year old mudstone contained complex hydrocarbons. This along with its detection of methane changes in the atmosphere are one step along the way to finding evidence of life on other planets. There have also been many more photos from the red planet, with Curiosity taking a few more selfies. See here how the car sized rover achieves the great pictures. On the other side of it there was a huge Martian storm that may have killed the Opportunity rover by covering the solar panels in dust. Although there are still hopes the rover can start communications again, we will have to see.

Curiosity in a dust storm
An image shared by Seán Doran on Sunday of the Mars Curiosity in the middle of a dust storm reported to cover an area the size of the US and Russia Combined. CredIt: NASA/JPL/Seán Doran.

Asteroid Rovers

In late september, another great story came out, that JAXA (the Japanese space agency) successfully landed a number of rovers on an asteroid. Still to launch all of the four onto the surface, there are already great images from the surface of an asteroid. The little rovers use a hopping mechanism to get around, as the gravity on the asteroid is so small a wheeled rover just wouldn’t work. The spacecraft will also be attempting to collect samples to return to Earth in the coming years. The Hayabusa 2 probe is a follow up to the Hayabusa probe which was not a sample return. The second launched on December 3rd 2014 and rendezvoused with the near-earth asteroid 162173 Ryugu on the 27th of June 2018. Currently in the process of surveying the asteroid for a year and a half, it will depart in December 2019, returning to Earth in December 2020.

 MINERVA-II image
First pictures from a MINERVA-II-1 rover that landed on the asteroid. Credit: JAXA.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts this year! So all have a Happy New Year, and here’s to a great 2019 in space!

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Operation Mincemeat: The Imaginary Man

Major Martin Identity card
One of the identity cards on Major Martins body when it was found.

The 1st of May 1943, the height of the second world war. Early in the morning on a spanish beach, a fisherman found a waterlogged corpse. Not an uncommon thing to find at this time it looked like he had washed ashore during the night. The dead body was a man dressed in British military uniform wearing a life jacket and suspiciously he had a briefcase chained to his arm. Reported as a casualty of an airplane accident at sea the body was moved to a local port where Nazi officials in the city of Huelva took possession of it. From the items on the body they identified him as Major William Martin, a temporary captain acting major in the British Royal Marines. The German intelligence organisation (the Abwehr) decided to break open the briefcase to examine the contents, but did contemplate letting it go on intercepted. Along with personal effects they found personal correspondence between Lt. Gen. Sir Archibald Nye, vice chief of the Imperial General Staff, and Sit General Harold Alexander, the British commander of North Africa. The letters described key details of plans to invade Nazi Held territory. It seemed like Germany now had the upper hand, but all was not as it seemed. All part of the British Operation Mincemeat, this is not a christmas story.

Within days the news of the body being found in Spain got to the British military. The body was returned and buried with full military honours in Huelva. The spanish took longer to return the documents though. The British admiralty demanded their return, with emphasis on discretion due to their sensitive nature. The Spanish government had to respond as they were technically a neutral party, but they were sympathetic to the Nazi cause. Eventually the documents were returned to the British military, but not before the German Abwehr agents had teased open the sealed letters, photographed the entire contents of the briefcase, and then resealed the envelopes. The photographs made their was to Berlin to be carefully analysed. The German intelligence were wary of a ruse, and examined the other effects in great detail. His possessions included many normal items like a photograph and love letters from his fiance, a set of keys, recently used stubs for the theatre and a hotel bill. After the close inspection they believed the items were likely genuine. This indicated the letters he was transporting were also authentic. There was another letter from the Chief of Combined Operations to the Commander-in-Chief in the Mediterranean that indicated that Major Martin was carrying a letter too sensitive to be sent through normal channels. This was the apparently reason that he was flying, acting as a courier. An image of his body can be found here.

Major Martin's fiancee, but really an MI5 officer.
The image of Major Martin’s fiancee found in the briefcase.

By all appearances the Axis powers had stumbled upon some extremely valuable intelligence, and they thought that the Allies were unaware. This, a letter indicating the exact beaches that the Allies were planning to use to invade, beaches the Axis powers could divert troops and reinforcements. The plan in the letters was described as “Operation Husky”, a secret plan to invade Nazi controlled Europe via Sardinia, Corsica and Greece. It also described a false attack upon Sicily, to draw German forces away from the “true” invasion site. Up to this point the Germans expected the Allies would invade via Sicily. Upon learning of the letter, Adolf Hitler took action. On May 12th he sent an order: “Measures regarding Sardinia and the Peloponnese take precedence over everything else.” This order diverted significant defences away from Sicily to the landing points indicated in the letter. These defences included an extra Waffen SS brigade, several Panzer divisions, patrol boats, minesweepers and minelayers. The thing is, the attacks never came to Sardinia, Corsica or Greece. The German intelligence had been duped by an elaborate deception designed to draw the Nazi defences away from the true target: Sicily. Major Martin, the dead man with the briefcase never existed.

Adm. John Godfrey
Adm. John Godfrey, the British director of naval intelligence, crafted the idea for Operation Mincemeat with the help of Lt. Cmdr. Ian Fleming. When Fleming went on to create the world of James Bond, it was rumored that the character M was based off of Godfrey. Credit: Imperial War Museum

The idea to plant false military documents on a dead man, who then fell into German hands was conceived by Lt. Cmdr. Ewen Montagu at British Naval Intelligence. He had built on an earlier idea proposed by Flight Lt. Charles Cholmondeley of the counter-intelligence service MI5. The original plan was to place a wireless radio on a dead soldier whose parachute was rigged to look like it had failed. The radio would then be a channel to provide disinformation to the enemy. This plan was deemed impractical, so the death at sea ruse conceived by Montagu was used instead, dubbed operation mincemeat. The Montagu team quietly procured the body of a 34 year old homeless man who had recently died of pneumonia. As his lungs already contained fluid like a drowned man’s would, it was perfect. As the body was waiting in storage his new identity was fabricated. MI5 had an operation known as the Twenty Committee, who had expertise in counter espionage. They were known as the XX, witch is the roman numeral for 20, but also refers to “double cross”. They gave the corpse identification, keys, personal letters, and other possessions. They attempted to show that Major Martin was an absent minded yet responsible chap, so as to explain the fact he had chained himself to the briefcase. They planted evidence such as overdue bills, and a replacement ID card to achieve this.

transporting Major Martin
Charles Cholmondeley and Ewen Montagu on 17 April 1943, allegedly transporting the body to Scotland.

On April 2th 1943, the new Major Martin was placed on the submarine HMS Seraph in a special steel canister packed with dry ice. The crew set of the coast of Spain, where a citizen of the Axis-aligned country would locate the body and report it to the authorities. After two days at sea the sub surfaced about a mile off the coast of Spain at 4:30 in the morning. The plan was so secret that the crew of the submarine believed the canister contained meteorological equipment, carrying it on deck. Then everyone went below, apart from the officers. There in the dark, Lt. Norman L.A. (Bill) Jewell, the commander of Seraph explained the plan, and the contents of the canister, swearing the men to secrecy. They then removed Major Martin from the canister, onto the deck. They then fitted a life jacket and chained the briefcase to him. They read the 39th Psalm and committed the body to the sea, where the tide could take him to shore. When discovered, the British requesting the swift return of the briefcase helped the illusion that the contents were important. To complete the illusion, Major Martin was even mentioned in the British Casualty list in the Times. When the British got the documents back they found tell tale signs that the letters were opened. They also intercepted German transmissions indicating the Nazi’s were moving forces towards Greece and Corsica. The news prompted a brief cable to Winston Churchill with the words “Mincemeat Swallowed Whole”.

Officers of HMS Seraph
The officers of HMS Seraph, the submarine selected for the operation, on board in December 1943. Credit: Royal Navy

On July 9th 1943 the Allied forces launched the real attack, Operation Husky. The plan struck the southern tip of Sicily, and the swiftly conquered the island. For the following two weeks the Germans still anticipated the landings in Sardinia and Greece, but they never came. By the time they realised of the trick, there was no time to regroup, so the forces retreated to Messina. It took a month to take control of the entire island. In the years afterwards there have been speculation of the true identity of Major William Martin. In 1996 an amateur historian, Roger Morgan wrote the book the Man Who Never Was. The book theorised that the body was of Glyndwr Michael, a Welsh vagrant. His official cause of death was of chemical pneumonia due to ingesting rat poison. The markings at his burial place in Heuva have been updated to show Glyndwr’s name on the tombstone. That being said, not everyone is convinced, as some pieces of the story don’t fit such as the time between his official death and the execution of Operation Mincemeat. Also the HMS seraph took a long detour before heading to the Spanish coast, which leads to the possibility the body was picked up elsewhere. There are theories that it could be a victim of an accident onboard the HMS Dasher. Due to the nature of the operation, and the efforts to protect the true identity it is unlikely we will ever find out who Major Martin was.

Thank You for reading, take a look at my other posts if you are interested in space, electronics, or any other sort of history. Alternatively follow me on Twitter to get updates on projects I am currently working on.

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Creating RAF Harwell

Some time in early 1935 there was a knock at the door of the bungalow stables near Chilton. Leonard Cundall opened the door to two uniformed men, with only one thing to say. “Mr Cundall there’s going to be a war”. Within 6 months the Air Ministry had compulsory purchased the land for £11,6500. The land would be used for one of many new airfields being built as part of a national war effort. The John Laing engineering company won the contract to build 66 airfields for the RAF expansion period prior to World War Two. Reportedly the area south of Harwell village had been used as an emergency landing ground for night flying since WW1. There has also been talk of the area being used as a glider training ground around this time as well. The ground is surprisingly flat, and a big open space, perfect for air training. The John Laing engineering company was also famous for building the Mulberry Harbour system, which was the artificial harbour built for the Normandy landings. They also build the Royal Ordinance factory in Sellafield, Windscale nuclear power plant, the M1, and the reconstruction of Coventry cathedral. Of the 66 airfields Laings company built, Harwell was the first to be constructed. The work started on the airfield in June of 1935. 

Paratroops of 22 Independent Parachute Company, British 6th Airborne Division, waiting to board the Armstrong Whitworth Albemarle Mk V that will drop them over Normandy, RAF Harwell, 5 June 1944. H 39065 War Office official photographers.

In RAF tradition all airfields have pretty much the same layout. This makes sense when you think about it as if a new pilot flies in from another group they know where to go to find the mess hall or where to get paid or where to find the Commanding Officer. Another tradition is that every building is numbered in the order of construction. No. 1 was the guardroom at the entrance to the site. After initial construction the site had 202 individually numbered buildings, and then almost another 100 houses on top of this for people to live. The hangars had a slightly different numbering system, the four hangars were originally named H1-H4, but at the outbreak of war they were renamed H7-H10. At the other end of the numbering B199 was a Gymnasium that doubled up as a chapel. There were no buildings west of Hangar 10 when the site was built. There was a gunnery range in this area that was there to realign the aircraft guns, but this was subsequently occupied by the B220 radio chemical facility, the first major building built by Chivers post war. Two civilian houses were demolished to make way for a a deep underground fuel store, building B3. It contained 6 large cylindrical tanks, with excavated dirt piled on top to produce bomb proof mounds. The second building was pulled down to become the main runway, which is now Frome Road. Aldfield farm to the north and Upper farm to the south escaped demolition. Upper farm stables were requisitioned though. The long building with large doors was perfectly sized to be turned into an aircraft cleaning shed. Go in one side dirty, come out the other side clean!

The Harwell site taken in 1944 with the A34 running from left to right at the top. According to the markings it was taken in April 1944.

The naming of the airfield comes with an interesting story. The 800 acre site sits mainly in the parish of Chilton. A third of the site is in East Hendred parish, with the smallest section being in Harwell. Up until the Commanding Officer got there, it likely had some sort of code name or number. When the CO arrived the subject of the name had to be handled. He lived in the largest of the houses in the northern end of the site in South Drive. He declared that the airfield should be named after whichever parish his house resided in. That parish happened to be Harwell, therefore RAF Harwell it was. As it was a very early airfield it had many flaws. Even worse, it was a bomber training station, with new and inexperienced pilots everywhere. The first big issue was that the three runways intersected in the middle (almost). This is a huge issue, as it would only take a single bomb to take out all three runways. Plus there is a much larger risk of the new pilots crashing in the centre when trying to launch at the same time. There was also a hugely complex system of taxi tracks. There were also over 120 dispersal pads for the planes/gliders scatted around the site. These pads are there to disperse parked aircraft, so if there is an air raid it will minimise the damaged caused overall. Also called hardstands, they also stopped damage to other planes if there was an accident while “bombing up”. These pads tended to be 150 ft (46 m) in diameter and at least 150 ft from the funnel track, this was actually a rule for all buildings on the site.

The pathfinders of the 22nd Independent Company and the Advance parties disembark from their trucks at RAF Harwell alongside the Albemarles of 295 Squadron that will carry them to Normandy. Copyright: Imperial War Museum.

One big thing that they overlooked in the design was the location of the munitions dump. They placed it at the end of the shortest runway, now known as Severn Road. The other issue with this particular runway is that it had a slight hill. When going along the runway you couldn’t actually see the other end over the brow of the hill. There are many stories of young pilots with huge bomb payloads barreling down the runway to then realise they did’t have enough speed to make it. They would have to ‘prang’ the aircraft into the field between the end of the runway and the bomb store fence. There was no reports of any explosions caused by this though. One other notable point is the building materials used in the construction of many of these buildings and tracks. The runway of a bomber station was often up to 9 inches (23 cm) thick, and took 18,000 tons of dry cement and 90,000 tons of aggregate, then covered with a layer of asphalt. In later airfields the hardcore used was often from destroyed buildings, and were carried by train to the sites. Harwell initially opened in February 1937 with a grass airfield but got replaced with concrete runways between July and August 1941.

A slightly better quality photograph of RAF harwell, you can clearly see the dispersal pads and the concrete runways. 

The buildings themselves were made from the classic red brick but the food preparation and storage areas were made from a brick named ‘grano’. Short for granolithic stone it was a mixture of sand cement and granite dust. The resulting stone was hard wearing and was perfect for the constant cleaning and wiping of food storage areas. The issue found later was that the high granite content meant measurable amounts of natural uranium/thorium. The food areas were slightly radioactive. They were also found in the walls of offices in the aircraft hangers and in the BISO, the aimens mess! Plus most dials on compasses and equipment were painted with radium, another radioactive material. Turns out Harwell always had some radioactive heritage.

A Short Stirling Mark IV (LK115, ‘8S-Z’) of No. 295 Squadron RAF, taking off from Harwell, Oxfordshire (UK), towing an Airspeed Horsa glider. Credit: Royal Air Force/ Imperial War museum

By the end of the war over 500 airfields had been built, and most of these issues were ironed out in later designs. The original site was only designed to last 10 years, but even today a huge amount of buildings on that Harwell site still remain in some state. There are a few sections of runway still left, and even a few of the dispersal pads are still visible underneath the undergrowth. 

Thank You for reading, take a look at my other posts if you are interested in space, electronics, or any other sort of history. Alternatively follow me on Twitter to get updates on projects I am currently working on.

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How to Define a Kilogram

So I recently read a great twitter thread by Max Fagin about the redefinition of the kilogram. It was on the news, and I saw a few TV segments about it, but I don’t think most appreciate the enormity of changing this basic building block of science. I learnt because if this story that there is a whole branch of science dedicated to the study of measurement, metrology. Metrologists ask and have answered the question, what actually is a unit of measurement? A weird question because we all probably have an idea in our head of what it means. If you are in the UK (or most of the world) then you would use a metre to measure distance, liters to measure volume, and kilograms to measure weight. In some parts of the world such as the USA then you may use gallons, feet, inches and pounds, but they all have to reference something. There are 2.2 pounds in a kilogram, 2.54mm in an inch but which one defines the other? Is it just a tangled mess of  interconnecting reliance?

It turns out it is not. All official units used in science (even the imperial units used in America) are defined in relation to the SI (Système International) unit definitions. They were established and have been maintained by the Bureau International des Poids et Mesures (BIPM) in France. It all starts with seven base units, and from them every other unit of measurement in existence can be defined. They are:

  • Kilogram, kg (mass)
  • Metre, m (distance)
  • Second, s (time)
  • Kelvin, K (temp)
  • Ampere, A (electric current)
  • Candela, cd (luminous intensity)
  • Mole, mol (quantity)

Every unit you have ever used is “officially” derived from these seven units. Ever used Watts? defined as 1 kg*m^2/s^3. 5 volts is officially 5 kg*m^2/(s^3*A). What about a gallon? Officially it is 0.003785 m^3. One atmosphere of pressure would seem simple enough until you realise it is 101325(kg/(m*s^2) of pressure.

Difference between the SI base units and the SI units that are derived from it. Image from @usnistgov

There is no standard foot, pound or gallon sitting in a vault in Washington or London, although they was at one point. All units are defined (also known as traceable) through the SI base units. But how do we define the 7 base units themselves? Well historically they are all based off of a thing, or artifact. For instance in the 1940’s 1 second was defined as 1/86400 the time it takes the Earth to rotate once. Then in the 1950’s it was redefined as 1/31556925.9747 the time it takes the Earth to orbit the sun. It took until the 1960’s for technology to advance far enough to redefine the second to something that isn’t an artifact (in this case the Earth). The time it takes the Earth to orbit the sun changes over time, it may be a long time, but it does change slightly. If the thing you are defining from changes, the thing you are using changes. If the Earth takes slightly longer to orbit the sun then the second becomes slightly longer. Although most of us don’t care, some very important science is based off of this very specific value.  Now it is based off of a fundamental property of the universe, something that doesn’t ever change. The fundamental property defining the second is the time it takes an electron in a cesium-133 atom to oscillate 9,192,631,770 times. As current science believes that the oscillations of electrons are constant properties of the universe the definition is now good forever.

The new caesium fountain atomic clock NPL-CsF3 becomes operational, allowing continuous operation of a primary clock at NPL. Work continues on the next generation of optical atomic clocks at NPL, which should achieve accuracies equivalent to losing or gaining one second in the age of the universe. Credit: NPL

The metre had a similarly long journey. British and BIPM spelling is metre, and American is meter. First it was defined as 1/10,000,000 of the distance from the equator to the north pole, but then they realised that the Earth surface is not consistent, and is definitely not constant. The Earth’s shape will change over time. So then they defined it as the distance between two marks on a platinum-iridium bar in France, literally an artifact. The bar was 90% platinum and 10% iridium, and was measured at the melting point of ice. This original bar is still kept under the conditions specified at it’s creation in 1889. In the 1980’s timing equipment became precise enough to move away from this artifact based definition. The constant of the universe used is the speed of light in a vacuum, 299,792,458 m/s (roughly 300 million). Basically a meter is defined as the distance light travels in 1/299,792,458 of a second. As it is constant it can be measured literally anywhere in space and time and it would be exactly the same, so a good definition. It also relies on time being measured using a constant of the universe too.


Closeup of National Prototype Metre Bar No. 27, made in 1889 by the International Bureau of Weights and Measures (BIPM) and given to the United States, which served as the standard for defining all units of length in the US from 1893 to 1960

All of the other base SI units have been defined in some way based on constants in the universe, with some being more complex than others. That is all but the kilogram, the stubborn one that has up until this point eluded redefinition. For 129 years the kilogram has been defined as the mass of an artifact stored in a vault in France. It is called the International Prototype Kilogram. Made like the metre, it is 90% platinum and 10% iridium. Unlike time and distance there is no easy way to precisely measure mass. So every attempt up until this point of redefining the kilogram has not met the precision of just taking the IPK out of the vault and giving it a good measure every once in a while. This is somewhat frustrating to metrologists as over the past 100 years there is evidence that the IPK has actually changed in mass by losing some material. It has changed by about 50 micro grams compared to it’s replicas. This is an odd paradox because it was the only thing in the universe that cannot not be a kilogram. So if some technician or scientist dropped it or chipped it then the weight we define atoms would literally go up. The IPK always weighs 1 kg. This is equally annoying because so many other measurements are based on the kilogram. The Newton for instance is defined as the force needed to accelerate one kilogram by 1 m/s^2.

Mass drift over time of national prototypes K21–K40, plus two of the IPK’s sister copies: K32 and K8(41). All mass changes are relative to the IPK.

The new way to define the kilogram is very complex, and I honestly don’t understand the details, there are better sites out there to get the details of this. Essentially it is based on the Planck constant, a fundamental property of the universe. Basically it relates the energy of a photon to its frequency. If Because you can know the energy of the photon, you can know the mass, and this is then directly related to the frequency of that photon. This means the kilogram can be defined in terms of the metre, second and a few constants of the universe. This has been hypothesized for some time, but until this point the technology has not been good enough to measure the Planck constant to a  sufficient accuracy. The best way that we currently use to do this measurement is using something called a Kibble balance, previously known as a watt-balance. It uses the electric power needed to oppose the force of the kilogram. As current, and electrical potential are already defined by constants of the universe the Kibble balance, with extensive calibration, can define 1 kilogram in terms of current. When I say extensive I do mean it, there needs to be an extremely precise measurement of gravity at that point. This extra complexity does mean that most countries are unlikely to invest in such devices, for the moment. But this is an important time, all measurements we currently know of are now based on actual constants of the universe. Gone are the days where we have to take something out of a vault to calibrate our measuring devices. 

Thank You for reading, take a look at my other posts if you are interested in space, electronics, or any other sort of history. Alternatively follow me on Twitter to get updates on projects I am currently working on.

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Why The Moon Could Fuel Future Space Missions

A recent report funded and published by the United Launch Alliance outlines the the potential viability of mining the Moon for rocket fuel. At over 170 pages, it is quite a read but Philip Metzger, one of the authors wrote a good summary on his website. I thought I would try and make a similar summary here with slight more explanation, and where it fits into the future NASA plans of getting back to the Moon and going onward to Mars and beyond. It all revolves around water, or more specifically ice. For many years we thought the Moon was a baron rocky cold desert. The samples that the Apollo astronauts brought back from the Moon, and the Soviet Luna samples imply that there is no water in the rocks or regolith. The trace amounts of water found in the samples were assumed to be contamination. Although, in 2008, a study of the Apollo rock samples did show some water molecules trapped in volcanic glass beads. Also in 1978, Soviet scientists published a paper claiming the 1976 Luna 24 probe contained 0.1% water by mass. Plus the Apollo 14 ALSEP Suprathermal Ion Detector Experiment (SIDE) detected the first direct evidence of water vapor ions on March 7th 1971. None of these discoveries were taken as conclusive proof of water on the Moon at the time.

An image of the SIDE experiment from Apollo 14. It measured the energies and masses of positively charged ions near the surface of the Moon and also studied the interaction between the solar wind and the Moon as the Moon moved through the Earth’s magnetic field. Credit: NASA.

On September 24th 2009 it was reported that the Moon Mineralogy Mapper (M3) spectrometer on India’s Chandrayaan-1 spacecraft had detected water ice on the Moon. The map of the features show that there is more at cooler, higher latitudes, and in some deep craters. Basically, the parts of the Moon that see the least light like the poles and far into craters near the poles have managed to keep the water on and below the surface. This water is in a number of different states, some locked up in minerals, some in ice form, and others in OH form, not technically water but near. This has lead to a number of new possibilities of inhabiting the Moon and using its resources. This is why the United Launch Alliance funded a paper on the possible use of mining this water and using it as a future fuel source. By some estimates there could be as much as 10 billion tonnes of water on the Moon. The water could in theory be mined, and through electrolysis turned into hydrogen and oxygen, the fuel that got men to the Moon on the famous Saturn V.

Left side of the Moon Mineralogy Mapper that was located on the Chandrayaan-1 lunar orbiter. Credit: NASA

But you have to ask, why does it matter? the Moon is far away, and surely water is just useful for astronauts living on the Moon to survive. Well the report talks about the business case to use the water as fuel, in the form of hydrogen and oxygen. First we need to understand the commercial satellite world, and geostationary satellites. When first sending up such satellites, the way to do it was to use a multi stage rocket, with the first stage getting to a Geostationary Transfer Orbit (GTO) and then the second (upper) stage being used to get into the Geostationary Orbit (GEO). Recent years have allowed the first stage to be hugely improved and often reusable by companies like SpaceX and Blue Origin. The second stage hasn’t had the same improvements though. Traditionally the second stage was a normal, and very heavy liquid rocket. This meant that it was very expensive to get things to GTO, much more difficult than LEO. The rocket was also thrown away afterwards, and as it is so far out it will take hundreds or even thousands of years to burn up in the atmosphere. 

A diagram of the traditional way to boost communication satellites into orbit. Credit Dr Phil Metzger

Now we do have a better way to do it, sort of. I talked recently about the rise of electric thrusters. A lightweight, cheap and powerful solution when used over a long period of time. Over the time span of years they can pick up speeds of thousands of miles per hour. That is the biggest downside of them though, in this situation, slowly pushing the satellite to orbit, they take up to a year to get a satellite into position. That is a year that it could be making the owner money. By some estimates that year could lose $100 million in revenue just waiting for the slow thrusters. By all accounts though, this is still cheaper than launching a large traditional rocket upper stage. The electric thrusters are amazingly light comparatively, which means you need a smaller first stage to get it up to space in the first place. The key thing you have to remember about these geosynchronous satellites is that they already have a huge price tag, some can cost upwards of half a billion dollars to build and launch.Part of the reason is that they tend to be huge, in size and weight. Some have been as big as London double Decker buses, and weigh 6 tonnes. The rockets then need to get them to one of the furthest and time consuming orbits, a costly exercise. 


A diagram of the current way to boost communication satellites into orbit. Credit Dr Phil Metzger

So why can this Moon mining idea help? well the Moon is in lots of countries space plans at the moment. China are currently sending lots of probes, and by some accounts looking to get humans there. The USA are building the SLS which should be able to get humans to the Moon, and are also developing the LOP-G idea. The concept to have an orbital station around the Moon, almost like a fuel stop for rockets going on to further parts of the solar system. This idea to mine the Moon for hydrogen and oxygen could be transferred up to this orbital space station to be transferred to the rockets that need it. This is where the geosynchronous satellites come in. Imagine if this fuel, that is dug up and processed by robots, and then sent up to an orbital station could be brought back closer to Earth via a space tug. This space tug could meet up with the rocket with the satellite on board. The upper stage rocket could have been sent up with no fuel (the heaviest bit) and is fueled by this space tug. It would allow for the speed of the old style engines, but the weight of newer electric engines. As long as the price for this whole system is cheaper than the $100 million it currently costs, then it could be a viable option. All the while, setting ground work for space agency’s to have viable water sources that can be used for future exploration. It may be the future of space travel.

Atlas 5 taking off
Atlas 5 lifting off from pad 41 at Cape Canaveral Air Force Base. If this idea takes off, these rockets could propel much larger payloads into much bigger orbits. Credit: @marcuscotephoto on Twitter

Thank You for reading, take a look at my other posts if you are interested in space or electronics, or follow me on Twitter to get updates on projects I am currently working on.

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Where Did the Ending of First Man Come From

For those out there who love space and the history behind it, of which I count myself, Damien Chazelle and Ryan Gosling have created First Man. The film follows the life of Neil Armstrong on the run up to the Apollo 11 landings where he became the first man to step foot on the Moon. All in all a great film, with lots of historical facts for those who know where to look. Beyond the few big plot points that Chazelle took minor liberties with, it gives a good account of run up to a huge moment for human engineering. The thing this post is focused on though, was the ending accurate, did Neil Armstrong actually throw his daughters bracelet into the crater.

A promotional still from the First Man film of Ryan Gosling as Neil Armstrong.

On the 20th of July 1969, Neil Armstrong and Buzz Aldrin spent 2 hours and 31 minutes exploring the lunar landscape, conducting experiments and collecting samples. All of it was scripted by NASA, practiced down to the last minute. There was a moment though where Neil took a short deviation from the plan, and that did actually happen. He wandered over to an area known as Little West Crater and took a moment there. It is not publicly known what happened at the edge of the crater, whether he was just reflecting, or like in the movie he may have thrown something into it. Either way it is unclear what actually happened, but some effort has been made to find out, mainly by the author of the First Man official biography in 2012, James K. Hansen.

The front cover of the book First Man. The official biography of Neil Armstrong, written by James R. Hansen.

Hansen spent four years researching the book about Armstrong, speaking to Neil himself and most of his family including his ex-wife Janet, Sister June and his children Eric and Mark. Throughout the interviews he develops a hunch that Neil may have left something on the Moon. This isn’t a crazy idea either because the astronauts did leave sentimental items on the Moon. On that very mission Buzz Aldrin left an Apollo 1 mission patch to commemorate the lost astronauts in the fire. The 10th person on the Moon, Charlie Duke left a photo of his family on the surface in 1972.

One of the photographs taken of the picture of Charlie Dukes family left on the lunar surface. Part of the Apollo archived photos. Credit: NASA

The big question is if he ever took the bracelet in the first place. If he did he wouldn’t have just snuck it on, it would be in the manifest known as the personal property kit (PPK) and Neil had a copy of this. When probed by Hansen he claimed to have lost the document, but on his death in August 2012 all of his archives were donated to his Alma mater Purdue University, and the document was part of it. The archives are under seal until 2020. When Hansen asked his sister June whether she thought he left something on the Moon for Karen she said “Oh I hope so”. Some may see the ending as a dreamt up Hollywood-ised version of the Moon landing. The decision not to add in the planting of the flag upset many Americans, and labeled the film as un-american. For me though, the scene when he steps foot upon the Moon is more important. That is the moment people remember, the bit that really counted. Plus the flag was included in the film, just not the planting of it.

A promotional still from the First Man movie, with Ryan Gosling as Neil Armstrong on the lunar surface with the sun visor down.

On a final note, I really liked some of the additions the film made. I loved the bit at the start where Chuck Yeager, who famously disliked Armstrong, grounded him. There were lots of tidbits and facts that were added in just to show that they had done their research. There were some inconsistencies, his daughter actually died well before that exact X-15 flight that got him grounded. There was also a famous point where Armstrong had to eject from the flying bedstead which got him in trouble. He is seen to be talking and arguing after, but in real life he had bit his tongue and could speak for days. Also, after the Apollo 1 fire the administrator, James Webb resigned, whereas they don’t seem to change the character in the films to make it simpler. These are not really massive plot problems though, they make little difference to the story, and don’t change our view of him. The minor changes made the film flow better, and those who care know the issues. Overall, it is a film people need to see.

Ryan Gosling as Neil Armstrong in First Man, just after he crashes the flying bedstead, in real life he bit his tongue so badly that he couldn’t speak for days after.

Thank You for reading, take a look at my other posts if you are interested in space or electronics, or follow me on Twitter to get updates on projects I am currently working on.

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The Geeky Geological Features of Charon

As talked about in a previous post, Charon was named after the wife if the discoverer James Christy. Since then the New Horizons probe has visited and taken some amazing pictures of the surface. As part of the mapping they have also started naming some of the craters and other geological features found on the surface, and they all have very fictional culture names. Although some have been accepted but he International Astronomical Union, there are still many that haven’t. As of April 2018 they have set out an agreed naming convention and set of rules for the names. They should conform to one of the following:

  • Destinations or milestones of fictional space and other exploration.
  • Fictional and mythological vessels of space or other exploration.
  • Fictional and mythological voyagers, travelers and explorers.
  • Authors and artists associated with space exploration, especially Pluto and the Kuiper Belt.

So far there have been many provisional names given by the New Horizons team based on mostly science fiction franchises such as Star Wars, Star Trek, Doctor Who and Firefly. Most are still provisional, but some have been accepted

Charon Enhanced
An enhanced colour version of Charon taken by New horizons space probe. It is enhanced to show the differences in surface composition. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

A Terra is a large landmass or highland, and there is only one highland region on Charon. It was named Oz Terra after the Wonderful Wizard of Oz children’s novel by L. Frank Baum. The dark spots on the surface are called maculae in planetary science. The first is named Gallifrey Macula after the home planet of Doctor Who (Gallifrey). The second is the Mordor Macula after the base of Sauron in the Lord of the rings books by J.R.R. Tolkien. A planum is a scientific name for a plateau (elevated plain) and Charon only has one. Named Vulcan Planum after the home planet of Spock in the Star Trek Series. Terrae, Maculae and Plana are all being named after fictional destinations. A Mons is a planetary mountain, you may have heard of some of the Mons currently being explored by NASA rovers on Mars. Charon has three major mountains and are named after authors and artists. Butler Mons is named after Octavia E. Butler, an american science fiction author. Clarke Montes is named after Arthur C. Clarke, a famous English science fiction author who wrote 2001: A Space Odyssey. Kubrick Mons is named after Stanley Kubrick, a film director of films such as the shining and clockwork Orange. All three of the Mons names are accepted by the IAU.

Mordor Macula is located at Charon. A large dark area about 475 km in diameter near the north pole of Charon, Pluto’s largest moon. It is named after the shadow lands in J.R.R. Tolkien’s The Lord of the Rings.  It is not currently known what Mordor is. It may be frozen gases captured from Pluto’s escaping atmosphere, a large impact basin, or both. Credit: NASA

A chasma is a deep steep sided depression (a chasm), and are being named after fictional vessels. Argo Chasma is named after a ship in the Greek myth of Jason and the Argonauts, it is also the spaceship in the English translation of the Space Battleship Yamato anime series. Caleuche Chasma is named after the mythological ghost ship that travels the seas around Chiloé Island off the coast of Chile, collecting dead who then forever live aboard (much like Davy Jones). Mandjet Chasma is named after the solar boat of the ancient Egyptian God Ra. All three of the above Chasmas are recognised by the IAU. Macross Chasma is named after the SDF-1 spaceship in the Macross anime series. Nostromo Chasma should be known to most as the spaceship in the Alien films. Serenity Chasma is from the spaceship used in the Firefly series. Tardis Chasma is named after the infamous blue box flown by Doctor Who.

Annotated map of Charon, with provisional names for features. Credit: NASA/JPL.

There are 16 notable craters found on Charon’s surface, of which six have officially recognised names. They have all been named after characters associated with science fiction and fantasy. Dorothy Crater is named after the main character is the Wizard of Oz, also naming the only terra on Charon. Nasreddin crater is a sufi traveler from folklore. Nemo is after Captain Nemo from novels by Jules Verne. Pirx crater is the main character from the short stories by Stanislaw Lem. Revati Crater is named after the main character in the Hindu epic narrative Mahabharata. Sadako Crater is the adventurer who traveled to the bottom of the sea in the medieval Russian epic Bylina. All of the above craters have been officially recognised by the IAU. Alice Crater is named after the main character of the Lewis Carroll novels. Kaguyahime Crater is named after the princess of the Moon in Japanese folklore. Organa Crater is named after princess Leia in the Star wars films, along with Vader Crater, and Skywalker crater. Ripley Crater is one of the more studied craters and is named after the main character in the Alien films. Kirk Crater, Spock Crater, Sulu Crater, and Uhura Crater are all named after main characters in the Star Trek TV franchise.

Photo of Charon centered on Ripley Crater. Nostromo Chasma crosses Ripley vertically. Vader is the dark crater at 12:00, Organa Crater is at 9:00, Skywalker Crater at 8:00, Gallifrey Macula and Tardis Chasma at 4:00. Credit: NASA/JPL

Thank You for reading, take a look at my other posts if you are interested in space or electronics, or follow me on Twitter to get updates on projects I am currently working on.

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Notes From NASA’s Chief Scientist Jim Green’s Talk on The Search For Extraterrestrial Life

A few weeks ago my place of work, STFC, was lucky enough to host NASA’s chief scientist Jim Green for a talk titled “The search for life on Earth in space and time”. At the time of writing there is a version of the talk on University of Oxfords Facebook page. A really interesting talk for anyone interested in space, and our solar system. It also goes much more in depth that this post today and gives a real insight into current science of our solar system. A planetary scientist himself he talks about the planets in our solar system that could harbor life and those that might have done previously. I found it a real insight into what NASA’s goals are and where they are looking for signs of life. I personally enjoyed the talk as Jim Green hosts the “Gravity Assist” podcast made by NASA.

logo for NASA’s Gravity Assist podcast hosted by Jim Green. Credit: NASA.

The first real point he made was how to define what life is, which is a reasonable question. If you want to go out and find life on other planets, how do you know when you have found it? Spacecraft and astronauts need instruments and tools to detect things, and to build those instruments you need to know what they are looking for. The definition they came up with was that life needs three things, to metabolize, reproduce and evolve. This is a pain because it’s difficult to see any of those things directly. If you take just the metabolizing part and break it down it makes it a bit simpler, you need organics, the energy source, and water. You also need some way to get rid of waste. Plus we need to take into account time, you could have a fully habitable environment but not have life if it isn’t the right time.

The ingredients needed for life, a slide in the Jim Green Talk. Credit: NASA

Time is a really important factor, Earth has existed for 4.6 billion years, and it hasn’t always had life. They have been at least 5 mass extinction events in that time as well. To really see what is happening we need to look at how the sun has changed over that time, it is the thing in the solar system with the most effect on us. Since its birth 4.6 billion years ago it has brightened, with the luminosity increasing up to 25 or 30% by some estimates. We know that the Goldilocks region or habitable zone of a star exists where water can exist in all three states, but that depends on how big the star is and how bright it is, and therefore over time this Goldilocks region changes. This would make life simpler when looking for exoplanets, just work out where the habitable zone is and choose planets in it, unfortunately it isn’t that simple. 

A diagram of how the habitable zone of a star changes over time with different brightnesses. Credit: NASA

Let’s start off with Mercury, the closest planet to the sun. It is larger than the moon, but it isn’t large by any means. It has a magnetic field, it is nearly tidally locked and it is incredibly hot. It out gasses, and from Messenger data most scientists have agreed that it has never had a substantial atmosphere, so water is very unlikely to have existed there. The next candidate would be Venus, it is a similar size to the Earth after all. The Soviet Union Venera missions looked at the atmosphere and the temperature, and found it is extremely hot. The surface is hot enough to melt lead, and the pressure is 90 times that of our own planet. The NASA Magellan probe found it to be highly volcanic, with a very thick atmosphere. This means there is basically no chance of water, and makes Venus a bad choice for finding life today. Using some fairly interesting concepts, scientists have modeled what early Venus may have looked like and found it likely had water at some point, but the runaway greenhouse effect along with the lack of magnetic field has stripped all water away. That being said one day we could produce probes good enough to dig through the surface and look for signs of life below the ever evolving surface layer.

Five global views of Venus by the Magellan probe. Credit: NASA.

The next obvious choice is Mars, much larger than the Moon, but only about half the size of Earth. It’s a bit of a runt due to Jupiter. The asteroid belt between Mars and Jupiter is made of rocks that could have been a part of Mars, but Jupiter’s massive gravitational pull denied that. We also know that at some point in its life it had oceans that covered two thirds of the surface that could have been up to a mile deep in places. It then went through massive climate change, and it lost its magnetic field. That means the solar winds have stripped away the atmosphere and left a dry and arid surface. The pressure is about 1% that of Earth. Plus as it is fairly close to Earth it means that we can visit it fairly easily. From a number of missions including satellites and a number of rovers, we know that there are organic compounds on the surface, and likely water under the surface. Although not a guarantee of life it is a big hint. There a number of missions planned including ESA’s ExoMars, and NASA’s InSight and the 2020 rover. These missions are designed to drill into the surface and understand more about the planet, and what the water held.

True color image of Mars taken by the OSIRIS instrument on the ESA Rosetta spacecraft during its February 2007 flyby of the planet. Credit: ESA.

We talked about the habitable zone, but there is another line (or sphere technically) that planetary scientists use called the snow line. Lying somewhere in the Kuiper belt, it defines that liquid water cannot exist beyond it. For a long time that was thought to be true, but research has revealed that some moons have liquid water below their icy surface. In 1611 Galileo discovered some of Jupiter’s moons, and they have been visited and studied by the Juno and Galileo probe. All the moons at one point had an ice crust. Scientists have found that some moons such as IO, lost this crust and have become very volcanic and volatile. Ganymede, Callisto and Europa still have this ice crust. Only Ganymede and Europa have any signs of a watery ocean underneath the crust, but Ganymede is somewhat ruled out from having life because of its very cold temperatures. This leaves Europa in this Jupiter habitable zone. Slightly smaller than out moon, it has been shown to have watery geysers that reach 400 km above the planet. That would be equivalent to Earth geysers hitting the space station. From tests by Galileo data it has been shown to have twice as much water than on Earth. Plus it has been like that for 4.6 billion years, so that is a good indication that there could be microbial or even complex life below the surface. There is a mission planned to go to visit Europa called Europa Clipper.

An image showing the icy crust of Jupiter’s moon Europa. Europa is about 3,160 kilometers (1,950 miles) in diameter, or about the size of Earth’s moon. This image was taken on September 7, 1996, by the camera on board the Galileo spacecraft during its second orbit around Jupiter. Credit: NASA/JPL/DLR.

Then there is Saturn, which has had many studies, and the thing that stands out is the moon Enceladus. It is the moon that really drew NASA’s attention to the possibility of water on these distant moons. It also has geysers, coming from huge cracks in the southern hemisphere. They are huge walls or water just pouring out of the body. With it being only a small moon of around 300 km, it suffers from tidal forces. The water pours out less when it is closer to to Saturn, and more when it is further away (due to an elliptical orbit). This has been measured and shown, as the Galileo spacecraft actually flew through one of the geysers and didn’t know it. We have spacecraft that have literally tasted this water. About 98% of the water that comes out of the geysers falls back onto the moon, but that 2% escapes and forms an e-ring. The Cassini spacecraft also flew through these plumes and managed to measure some of this water, and more importantly small bits of rock. It gives indications of hydro thermal vents being the cause of these plumes of water.

NASA’s Cassini spacecraft captured this view as it neared icy Enceladus for its closest-ever dive past the moon’s active south polar region. Credit: NASA/JPL

Another spectacular moon of Saturn in the running is the famous Titan. It is bigger than the planet Mercury, the atmosphere is about twice that of ours, and is dominated by nitrogen. Trace gasses of methane and ethane have been detected, and it has large bodies of liquid. Radar images of the surface piercing through the thick atmosphere show rocky terrain and flat lakes of liquid methane. This has spurred on the idea that life could be very different, and could survive in such liquids as methane. So if we want a chance of finding life not like us then Titan would be the best place to go. There are a number of important missions that are planned to visit Titan and make much better measurements of the surface. Including robotic missions and maybe even very simple rovers. By all accounts it is still in early stages.

These six infrared images of Saturn’s moon Titan represent some of the clearest, most seamless-looking global views of the icy moon’s surface produced so far. The views were created using 13 years of data acquired by the Visual and Infrared Mapping Spectrometer (VIMS) instrument on board NASA’s Cassini spacecraft. Credit: NASA/JPL-Caltech/University of Nantes/University of Arizona

This data taken from these missions have allowed us to look further afield to find exoplanets that could fit what we now use to define habitable planets. Missions such as Kepler have refined the way to detect planets by looking at stars for long periods of time. looking at how stars dim and wobble when planets go in front if them. The big exoplanet mission for NASA currently is TESS. Launched in April it has gone through its commissioning and is already finding planets out there. The idea for it is to take large amounts of images over a long time and try to find as many exoplanets as possible. Hopefully producing thousands of potential planets, the best looking ones can then use much more powerful and advanced telescopes such as JWST to make better measurements and tease out the atmosphere and makeup of these exoplanets. One closing point that Jim Green made, when you go out and look at the stars at night, just remember that there are more planets on our galaxy than there are stars visible in the sky. 

One of the first images taken by NASA TESS, centered on the southern constellation Centaurus, reveals more than 200,000 stars. Credit: NASA.

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