Space Sunday: of molecules, meteorites and missions

In 1996, amidst a huge fanfare which included a statement by then US President Bill Clinton, a team of researchers announced they had discovered evidence of past Martian microbial life within a meteorite called ALH84001, discovered in the Allen Hills of Antarctica in 1984.

The claim lead to a high degree controversy, with many scientists disputing the findings of the original team. While that discovery has never been conclusively disproved, it has never been verified, either. However, it has – alongside the controversial results from two of the Viking Lander experiments in the 1970s – encouraged teams researching the potential for microbial life on Mars to be cautious in their work.

So it was with a sense of excitement that on Thursday, June 7th, 2018, NASA announced that the Mars Science Laboratory (MSL) Curiosity rover has once again found potential evidence of both organic molecules and methane on Mars. The news came via two papers Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars and Background levels of methane in Mars’ atmosphere show strong seasonal variations.

In the first paper, the authors indicate how Curiosity’s Sample Analysis at Mars (SAM) suite detected traces of methane in drill samples it took from Martian rocks in 2016. Once these rocks were heated, they released an array of organics and volatiles similar to how organic-rich sedimentary rocks do on Earth – where similar deposits are indications of fossilised organic life.

What is particularly exciting is the first paper indicates that the material discovered on Mars is similar to terrestrial kerogen, a solid organic matter found in sedimentary rocks. Comprising an estimated 1016 tons of carbon, Kerogen on Earth exceeds the organic content of all living matter on Earth by a factor of 10,000.

NASA’s Curiosity rover has discovered ancient organic molecules on Mars, embedded within sedimentary rocks that are billions of years old. Credit: NASA Goddard Space Flight Centre

Essentially, want happens on Earth is that organic material gets laid down within the sedimentary layers, then over the aeons, fluid flowing thought the rock initiates chemical reactions to break down the organic deposits until only the insoluble  kerogen is left. It has already been established that Gale Crater was once the home of several liquid water lakes, and also that perchlorate salt – particularly good at breaking down organics – is present on Mars. Hence why the discovery of the kerogen-like material on Mars is a cause for excitement – it could be a similar process to that seen on Earth is present.

While the team responsible for the styudy point out the material SAM has found is similar to an insoluble material discovered in tiny meteorites known to fall on Mars, that it might have formed naturally on the planet is somewhat strengthened by the fact Curiosity has previously confirmed Gale Crater contains the chemical building blocks and energy sources that are necessary for life. However, the legacy of ALH84001 urge caution when dealing with these findings from the rover, as one of the authors of the first paper explained.

Curiosity has not determined the source of the organic molecules. Whether it holds a record of ancient life, was food for life, or has existed in the absence of life, organic matter in materials holds chemical clues to planetary conditions and processes… The Martian surface is exposed to radiation from space. Both radiation and harsh chemicals break down organic matter. Finding ancient organic molecules in the top five centimetres of rock that was deposited when Mars may have been habitable, bodes well for us to learn the story of organic molecules on Mars with future missions that will drill deeper.

Jennifer Eigenbrode, co-author, Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars

In the second paper, scientists describe the discovery of seasonal variations in methane in the Martian atmosphere over the course of nearly three Mars years, which is almost six Earth years. This variation was also detected by Curiosity’s SAM instrument suite over the 3-year period.

This image illustrates possible ways methane might get into Mars’ atmosphere and also be removed from it. Credit: NASA Goddard Space Flight Centre / University of Michigan

Water-rock chemistry might have generated the methane, but scientists cannot rule out the possibility of biological origins. Methane previously had been detected in Mars’ atmosphere in large, unpredictable plumes. This new result shows that low levels of methane within Gale Crater repeatedly peak in warm, summer months and drop in the winter every year.

This is the first time we’ve seen something repeatable in the methane story, so it offers us a handle in understanding it. This is all possible because of Curiosity’s longevity. The long duration has allowed us to see the patterns in this seasonal ‘breathing.’

Chris Webster, co-author, Background levels of methane in Mars’ atmosphere show strong seasonal variations

In 2013, SAM detected organic molecules in rocks at the deepest point in the crater. These more recently findings, gathered further up the slopes of “Mount Sharp” add to the inventory of molecules detected in the ancient lake sediments. Thus, finding methane in the atmosphere and ancient carbon preserved on the surface gives scientists confidence that NASA’s Mars 2020 rover and ESA’s ExoMars rover will find even more organics, both on the surface and in the shallow subsurface.

NASA Successfully Transfers Sample

Following my last two Space Sunday updates concerning attempts to resume the collection of rock samples using Curiosity’s drilling mechanism, the US space agency has indicated a successful transfer of material gathered within the rover’s hollow drill bit into the rover’s on-board science suite (which includes the SAM instrument referred to above).

The new drilling capability is referred to as Feed Extended Drilling (FED), designed to bypass a formerly critical, but at risk of failure, piece of the rover’s drill system called the drill feed mechanism. This mechanism also used to form a part of the means by which samples used to be transferred from Curiosity’s arm-mounted turret to the on-board science suite. As it can no longer be used, engineers instead determined the sample could potentially be transferred to the science suite by positioning the drill bit directly over the sample intake ports and then running the drill in reverse, causing the gathered sample to (hopefully) trickle backwards and into one of the hoppers.

Referred to as Feed Extended Sample Transfer, the approach was tested on May 31st, 2018, and successfully saw the transfer of part of a sample obtained on May 19th into the hopper serving the rover’s Chemistry and Mineralogy (CheMin) unit.

Curiosity’s drill bit (upper right) positioned over one of the sample inlets on the rover’s deck leading to the on-board science suite. This image was captured on May 31st, 2018 (Sol 2068) by the rover’s Mast Camera (Mastcam). Credit: NASA / MSSS

The approach had already been successfully tested on Earth, but there were concerns the thin, dry atmosphere of Mars might not produce the same results. There’s also a matter of balance. Previously, any sample gathered by the drill would pass through the rover’s CHIMRA sieving system, which helps ensure the right amount is transferred to the on-board instruments. Without this, transfers become a matter of judgement, as engineer John Moorokian explained following the transfer:

On Mars we have to try to estimate visually whether this is working, just by looking at images of how much powder falls out. We’re talking about as little as half a baby aspirin worth of sample.

John Moorokian, lead developer of the FEST delivery method

The problem here is, were too little materials transferred, and CheMin and SAM would not be able to provide accurate analyses, but transfer too much of the unsorted material, and it could either clog instruments or remaining unused, potentially contaminating measurement of future samples. So far, it appears the first attempt has succeeded, although it will still be a while before the outcome of any analysis is known.
Continue reading “Space Sunday: of molecules, meteorites and missions”

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Space Sunday: drills, neutrinos and a spaceplane

In May I wrote about an attempt to return the drill mechanism on the Mars Science Laboratory (MSL) rover Curiosity to operational status. As I noted in that report, use of the sample-gathering drill was suspended in December 2016, after problems were encountered with the drill feed mechanism – the motor used to extend the drill head leading to fears that continued use of the drill feed mechanism would see it fail completely, ending the use of the drill.

At the time of that report, a live test of the drill on Mars had just been carried out, but the results hadn’t been made public. However, on May 23rd, NASA issued an update confirming the test had been successful, and a sample of rock had been obtained.

The new drilling technique is called Feed Extended Drilling (FED). It keeps the drill head extended and uses the weight of the rover’s robot arm and turret to push the bit into a target rock. This is harder than it sounds, as it requires the weight of the rover’s arm to provide the necessary pressure to help push the drill bit into a rock – something it is not designed to do, and risks either breaking the drill bit or cause it to become stuck.

Engineers had spent more than a year developing the technique using Curiosity’s testbed “twin” on Earth before carrying out a preliminary test on Mars in February (see here), which was not intended to gather any sample. For the May 19th, 2018, test the mission team combined the FED approach to drilling with using the drill’s percussive mechanism with the intention of both testing the combined technique with an attempt to obtain a sample of rock.

The sample in question is of specific importance to the mission team, although it required a literal turnaround for the rover. For the last few months, Curiosity has been traversing “Vera Rubin Ridge” on “Mount Sharp”. In doing so, the rover passed a distinct rock formation mission scientists realised could fill a gap in their understanding about how “Mount Sharp” may have formed. However, at the time, there was no way to obtain a sample. Once it looked likely that drilling operations could be recovered, the decision was made in April to reverse the rover’s course and return to the rock formation, where the test was successfully carried out.

The team used tremendous ingenuity to devise a new drilling technique and implement it on another planet. Those are two vital inches of innovation from 60 million miles away. We’re thrilled that the result was so successful.

– Curiosity Deputy Project Manager Steve Lee.

The 5 cm (2-in) deep hole in a target called “Duluth”, captured by the rover’s Mastcam on May 20th, 2018 (Sol 2057) after a successful test allowed a rock sample to be gathered by the rover since October 2016. Credit: NASA/JPL / MSSS

The rover has since resumed its traverse towards an uphill area enriched in clay minerals that the science team is  also eager to explore. The next stage for the engineers it so figure out how to transfer the gathered sample ready for analysis by the rover’s on-board laboratory.

Previously, this would have involved passing the sample through another system on the rover’s “turret”, called CHIMRA (Collection and Handling for In-Situ Martian Rock Analysis). However, transfer into CHIMRA in part requires the use of the drill feed mechanism. As this can no longer be used in case it breaks. the idea – yet to be tested – is to try positioning the drill head over the hoppers feeding the science suite and then running the drill in reverse, allowing the sample  – held within the hollow drill bit – to trickle back out, and hopefully into the hoppers.

If It’s A Particle Jim, Then It’s Not As We Know Them

Neutrinos are elementary particles that interact only via the weak subatomic force and gravity. Their behaviour is explained by the Standard Model of particle physics.

In essence – and very broadly speaking – the Standard Model is a list of particles that go a long way toward explaining how matter and energy interact in the cosmos. Some of these particles – quarks and electrons, for example – are the building blocks of the atoms that make up everything we’ll ever touch with our hands. Others, like the three known neutrinos, are more abstract: high-energy particles which can be created naturally (within the core of stars or during supernova events, for example), or artificially (e.g. in nuclear reactors or nuclear explosions), and which stream through the universe, barely interacting with other matter. Billions upon billions of solar neutrinos pass through each of us every second without ever affecting us.

The LSND. Credit: Los Alamos National Laboratory

These neutrinos can be broken into three known “flavours”:  electron, muon and tau neutrinos. As waves of neutrinos stream through space, they periodically “oscillate,” jumping back and forth between one flavour of the three flavours and another – or that’s the theory.

In the 1990s, the Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos National Laboratory, New Mexico, reported more neutrino detections than the Standard Model’s description of neutrino oscillation could explain, resulting in a new flavour of “heavy” neutrino being posited: the “sterile neutrino”.

At the time, the discovery met with excitement; physicists had long noticed a discrepancy between the predicted and actual number of anti-neutrinos, or the antimatter partners to neutrinos, produced in nuclear reactors. Sterile neutrinos could offer an explanation for the discrepancy. The only problem with the idea is that other than the LSND results, no-one has been able to find evidence for the existence of “sterile neutrinos”.

Until, possibly, now. A paper just published suggests that another neutrino detector – the MiniBooNE, operated Fermilab in Chicago – has also reported a similar result to LSND, resulting in the suggestion some neutrinos are oscillating into the “heavier” sterile neutrinos and then back into one of the recognised flavours. What’s more, combining the results of the MiniBooNE experiment with those of LSND suggests there is just a one-in-500 million chance of both results being a fluke.

Continue reading “Space Sunday: drills, neutrinos and a spaceplane”

Space Sunday: drills, telescopes, pictures and doubts

In March I reported that NASA’s Mars Science Laboratory rover Curiosity had taken an important step in recovering its ability to drill into Martian rocks to collect samples. Now it looks like drilling operations could be resuming.

Use of the sample-gathering drill was suspended in December 2016, after problems were encountered with the drill feed mechanism – the motor used to extend the drill head between two “contact posts” designed to steady the rover’s turret during drilling operations. In particular, there was concern that continued use of the drill feed mechanism would see it fail completely, ending the use of the drill.

Since then, engineers have been trying to develop a means of using the drill without and reliance on the drill feed mechanism, and at the end of February 2018, a new technique was tested. Called Feed Extended Drilling, or FED,  it keeps the drill bit and head extended, and uses the weight of the rover’s robot arm and turret to push the bit into a target rock. This is harder than it sounds,as it requires the weight of the rover’s arm to provide the necessary pressure to help push the drill bit into a rock – something it is not designed to do, and might actually break the drill bit or cause it to become stuck. However, the rover passed the February test with flying colours.

This success meant that engineers could focus on recovering the drill’s percussive action. This assists in both helping the drill cut into a rock and in breaking the contact area under the bit up into a fine powder that can be collected by the collection tube surrounding the bit.

A close-up of the drill mechanism. In the centre is the hollow drill bit, which cuts into rock and gathers sample powder. The drum at the base of the drill is the first part of the sample collection mechanism. Also of this used to be extended up against a rock sample by the drill feed mechanism. Just visible cutting across the bottom right corner of the image is one of the two contact posts. The second post can be seen in part in the top right corner of the image. These are used to hold the rover’s robot arm steady against a target rock surface while the drill is extended for sample-gathering operations. Credit: NASA

On Saturday, May 19th, and following further tests using Curiosity’s Earth-base test bed twin, the command was sent to Mars for Curiosity to carry out a second drilling test using both the FED approach and with the drill percussive action enabled. Unlike the February test, however, this one has an additional goal: to actually recover a special sample of rock.

For the last couple of months, the rover has been making its way along a feature on “Mount Sharp” dubbed “Vera Rubin Ridge”, toward an uphill area enriched in clay minerals that the science team is eager to explore. In doing so, the rover passed a distinct rock formation that could fill a gap in the science team’s knowledge about Mount Sharp and its formation.

Testing the FED / percussion approach to drilling on Earth using Curiosity’s test-bed “twin”. Not how the drill head (centre) is fully extended, so the contact posts cannot be used. Forward pressure on the drill is being provided entirely by the rover’s robot arm. Credit: NASA/JPL

Given the progress made in trying to get the drill working again, the decision was made to reverse Curiosity’s course in mid-April and drive back to the rock formation in the hope that the May 19th test could gather a sample from it. Commenting on the decision, Curiosity principal scientist Ashwin Vasavada  said, “Every layer of Mount Sharp reveals a chapter in Mars’ history. Without the drill, our first pass through this layer was like skimming the chapter. Now we get a chance to read it in detail.”

If the new technique has allowed Curiosity to gather a sample – at the time of writing this article, NASA had yet to provide an update on the operation – the engineering team will immediately begin testing a new process for delivering that sample to the rover’s internal laboratories. This is again a complex process, which in the past has involved the drill feed mechanism to transfer material gathered by the drill to another mechanism called CHIMRA (Collection and Handling for In-Situ Martian Rock Analysis), also mounted on the rover’s turret. CHIMRA sieves and sorts the material, grading it by size and coarseness before transferring it to the rover’s science suite, located in Curiosity’s main body.

Curiosity’s “fingers”: the five instruments on the rover’s turret, including the drill with the feed mechanism motors behind it and the two angled contact posts clearly visible, and the CHIMRA system used for sieving and sorting sample material gathered by both its own scoop (for surface material) and the drill (for rock samples). Credit: NASA 

Success with both the drilling operation and same transfer will mean – allowing for fine-tuning and other adjustments – the drill could be re-entering regular use in the near future.

Continue reading “Space Sunday: drills, telescopes, pictures and doubts”

Space Sunday: drills, flares and monster ‘planes

NASA’s Mars Science Laboratory (MSL) rover Curiosity has taken a further step along the way to retrieving and analysing samples gathered by its drill mechanism, which hasn’t been actively used since December 2016, after problems were encountered with the drill feed mechanism.

Essentially, the drill system is mounted on Curiosity’s robot arm and uses two “contact posts”, one either side of the drill bit, to steady it against the target rock. A motor – the drill feed mechanism – is then used to advance the drill head between the contact posts, bringing the drill bit into contact with the rock to be drilled, and then provide the force required to drive the drill bit into the rock. However, issues were noted with this feed mechanism, during drilling operations in late 2016, leading to fears that it could fail at some point, leaving Curiosity without the means to extend the drill head, and thus unable to gather samples.

To overcome this, MSL engineers have been looking at ways in which the feed mechanism need not be used – such as by keeping the drill head in an extended position. This is actually harder than it sounds, because the drill mechanism – and the rover as a whole – isn’t designed to work that way. Without the contact posts, there was no guarantee the drill bit would remain in steady, straight contact with a target rock, raising fears it could become stuck or even break. Further, without the forward force of the drill feed mechanism, there was no way to provide any measured force to gently push the drill bit into a rock – the rover’s arm simply isn’t designed for such delicate work.

Curiosity’s drill mechanism, showing the two contact posts (arrowed) used the steady the rover’s robot arm against a target rock, and the circular drill head and bit between them – which until December 2016, had been driven forward between the two contact posts by the drill feed mechanism, which also provided the force necessary to drive the drill bit into a rock target. Credit: NASA/JPL / MSSS

So, for the larger part of 2017, engineers worked on Curiosity’s Earth-based twin, re-writing the drill software, carrying out tests and working their way to a point where the drill could be operated by the test rover on a “freehand” basis. At the same time, code was written and tested to allow force sensors within the rover’s robot arm – designed to detect heavy jolts, rather than provide delicate feedback data – to ensure gentle and uniform pressure could be applied during a drilling operation and also monitor vibration and other feedback which might indicate the drill bit might be in difficulty, and thus stop drilling operations before damage occurs.

At the end of February 2018, the new technique was put to the test on Mars. Curiosity is currently exploring a part of “Mount Sharp” dubbed “Vera Rubin Ridge”, and within the area being studied, the science team identified a relatively flat area of rock they dubbed “Lake Orcadie”, and which was deemed a suitable location for an initial “freehand” drilling test. The rover’s arm was extended over the rock and rotated to gently bring the extended drill head in contact with the target, before a hole roughly one centimetre deep was cut into the rock. This was not enough to gather any samples, but it was sufficient to gauge how well robot arm and drill functioned.

“We’re now drilling on Mars more like the way you do at home,” said Steven Lee, a Curiosity deputy project manager on seeing the results of the test. “Humans are pretty good at re-centring the drill, almost without thinking about it. Programming Curiosity to do this by itself was challenging — especially when it wasn’t designed to do that.”

The test drill site of “Lake Orcadie”, “Vera Rubin Ridge”, imaged by Curiosity’s Mastcam on February 28th, 2018, following the initial “freehand” drilling test. Credit: MASA/JPL / MSSS

The test is only the first step to restoring Curiosity’s ability to gather pristine samples of Martian rocks, however. The next test will be to drive the drill bit much deeper – possibly deep enough (around 5 cm / 2 inches) to gather a sample. If this is successful, then the step after that will be to test a new technique for delivering a gathered sample to its on-board science suite.

Prior to the drill feed mechanism issue, samples were initially graded and sorted within the drill mechanism using a series of sieves called CHIMRA – Collection and Handling for In-Situ Martian Rock Analysis, prior to the graded material between deposited in the rover’s science suite using its sample scoop. This “sieving” of a sample was done by upending the drill and then rapidly “shaking” it using the feed mechanism, forcing the sample into CHIMRA. However, as engineers can no longer rely on the drill feed mechanism, another method to transfer samples to the rover’s science suite has had to be developed.

This involves placing the drill bit directly over the science suite sample ports, then gently tapping it against the sides of the ports to encourage the gathered sample to slide back down the drill bit and into the ports. This tapping has been successfully tested on Earth – but as the Curiosity team note, Earth’s atmosphere and gravity are very different from that of Mars. So whether rock powder will behave there as it has here on Earth remains a further critical test for Curiosity’s sample-gathering abilities.

More Evidence Proxima b Unlikely To Be Habitable

Since the confirmation of its discovery in August 2016, there has been much speculation on the nature of conditions which may exist on Proxima b, the Earth-sized world orbiting our nearest stellar neighbour, Proxima Centauri, 4.25 light years away from the Sun.

Although the planet – roughly 1.3 times the mass of Earth – orbits its parent star at a distance of roughly 7.5 million km (4.7 million miles), placing it within the so-called “goldilocks zone” in which conditions might be “just right” for life to gain a foothold on a world, evidence has been mounting that Proxima b is unlikely to support life.

Comparing Proxima b with Earth. Credit: Space.com

The major cause for this conclusion is that Proxima Centauri is a M-type red dwarf star, roughly one-seventh the diameter of our Sun, or just 1.5 times bigger than Jupiter. Such stars are volatile in nature and prone stellar flares. Given the proximity of Proxima-B its parent, it is entirely possible such flares could at least heavily irradiate the planet’s surface, if not rip away its atmosphere completely.

This was the conclusion drawn in 2017 study by a team from NASA’s Goodard Space Centre (see here for more). Now another study adds further weight to the idea that Proxima b is most likely a barren world.

In Detection of a Millimeter Flare from Proxima Centauri, a team of astronomers using the ALMA Observatory report that a review of data gathered by ALMA whilst observing Proxima Centauri between January 21st to April 25th, 2017, reveals the star experienced a massive flare event. At its peak, the event of March 24th, 2017, was 1000 times brighter than the “normal” levels of emissions for the star, for a period of ten seconds. To put that in perspective, that’s a flare ten times larger than our Sun’s brightest flares at similar wavelengths.

An artist’s impression of Proxima b with Proxima Centauri low on the horizon. The double star above and to the right of it is Alpha Centauri A and B. The ALMA study suggests that it is very unlikely that Proxima b retains any kind of atmosphere, as suggested by this image. Credit: ESO

While the ALMA team acknowledge such ferocious outbursts from Proxima Centauri might be rare, they also point out that such outbursts could still occur with a frequency that, when combined with smaller flare events by the star, could be sufficient enough to have stripped the planet’s atmosphere away over the aeons.

“It’s likely that Proxima b was blasted by high energy radiation during this flare,” Meredith A. MacGregor, a co-author of the study stated as the report was published. “Over the billions of years since Proxima b formed, flares like this one could have evaporated any atmosphere or ocean and sterilised the surface, suggesting that habitability may involve more than just being the right distance from the host star to have liquid water.”

Which is a bit of a downer for those hoping some form of extra-solar life, however basic, might be sitting in what is effectively our stellar back yard – but exoplanets are still continuing to surprise us, both with their frequency and the many ways in which they suggest evolutionary paths very different to that taken by the solar system.

Continue reading “Space Sunday: drills, flares and monster ‘planes”

Space Sunday: Mars rover round-up

Curiosity, NASA’s Mars Science Laboratory (MSL) continues its exploration and examination of “Vera Rubin Ridge” on the slopes of “Mount Sharp”.

Most recently, star- and swallowtail-shaped tiny, dark bumps in fine-layered bright bedrock have been drawing the attention of the rover’s science team due to their similarity to gypsum crystals formed in drying lakes on Earth – although multiple possibilities for the features are being considered alongside their potential for being formed as a result of water action.

The features pose a number of puzzles: where they formed at the same time as the layers of sediment in which they sit, or were formed later as a result of some action? Might they have been formed inside the rock sediments of “Mount Sharp” and exposed over time as a result of wind erosion? Do they contain the mineral that originally crystallised in them, or was it dissolved away to be replaced by another? Answering these questions may point to evidence of a drying lake within Gale Crater, or to groundwater that flowed through the sediment after it became cemented into rock.

“Vera Rubin Ridge” stands out as an erosion-resistant band on the north slope of lower Mount Sharp inside Gale Crater. It was a planned destination for Curiosity even before the rover’s 2012 landing on the crater floor near the mountain. The rover began climbing the ridge about five months ago, and has now reached the uphill, southern edge. Some features here might be related to a transition to the next destination area uphill, which is called the “Clay Unit” because of clay minerals detected from orbit.

In addition to the deposits, the rover team also is investigating other clues on the same area to learn more about the Red Planet’s history. These include stick-shaped features the size of rice grains, mineral veins with both bright and dark zones, colour variations in the bedrock, smoothly horizontal laminations that vary more than tenfold in thickness of individual layers, and more than fourfold variation in the iron content of local rock targets examined by the rover.

A mineral vein with bright and dark portions distinguishes this Martian rock target, called “Rona,” near the upper edge of “Vera Rubin Ridge” on Mount Sharp. The MAHLI camera on NASA’s Curiosity Mars rover took the image after the rover brushed dust off the grey area, roughly 5cm by 7.5 inches. Click for full size. Credit: NASA/JPL / MSSS

The deposits are about the size of a sesame seed. Some are single elongated crystals. Commonly, two or more coalesce into V-shaped “swallowtails” or more complex “lark’s foot” or star configurations. They are characteristic of gypsum crystals, a form of calcium sulphate which can form when salts become concentrated in water, such as in an evaporating lake.

“These tiny ‘V’ shapes really caught our attention, but they were not at all the reason we went to that rock,” said Curiosity science team member Abigail Fraeman of NASA’s Jet Propulsion Laboratory. “We were looking at the colour change from one area to another. We were lucky to see the crystals. They’re so tiny, you don’t see them until you’re right on them.”

“There’s just a treasure trove of interesting targets concentrated in this one area,” Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory, adds. “Each is a clue, and the more clues, the better. It’s going to be fun figuring out what it all means.”

In January, Curiosity examined a finely laminated bedrock area dubbed “Jura”, thought to result from lake bed sedimentation, as has been true in several lower, older geological layers Curiosity has examined. This tends to suggest the crystals formed as a lake in the crater evaporated. However, an alternate theory is that they formed much later, as a result of salty fluids moving through the rock during periodic “wet” bouts in the planet’s early history. This would again be consistent with features previous witnessed by Curiosity in its past examination of geological layers, where subsurface fluids deposited features such as mineral veins.

The surface of the Martian rock target in this stereo, close-up image from the Curiosity rover’s MAHLI camera includes small hollows with a “swallowtail” shape characteristic of gypsum crystals. The view appears three-dimensional when seen through blue-red glasses with the red lens on the left. Click for full size. Credit: NASA/JPL / MSSS

That the deposits may have formed as a result of fluids moving down the slopes of “Mount Sharp” is pointed to by some of them being two-toned – the darker portions containing more iron, and the brighter portions more calcium sulphate. These suggest the minerals which originally formed the features have been replaced or removed by water. The presence of calcium sulphate suggests salts were suspended in any water which may have once been present in the crater. If this is the case, it could reveal more about the past history of Mars.

“So far on this mission, most of the evidence we’ve seen about ancient lakes in Gale Crater has been for relatively fresh, non-salty water,” Vasavada said. “If we start seeing lakes becoming saltier with time, that would help us understand how the environment changed in Gale Crater, and it’s consistent with an overall pattern that water on Mars became more scarce over time.”

Even if the deposits formed inside the sediments of “Mount Sharp” and were exposed over time as a result of wind erosion, it would reveal a lot about the region, providing evidence that as water became more and more scarce, so it moved underground, taking any minerals which may have been suspended within it along as well.

“In either scenario – surface or underground formation –  these crystals are a new type of evidence that builds the story of persistent water and a long-lived habitable environment on Mars,” Vasavada notes.

As well as offering further evidence of Gale Crater having once being the home of multiple wet environments, the presence of iron content in the veins and features might provide clues about whether the wet conditions in the area were favourable for microbial life. Iron oxides vary in their solubility in water, with more-oxidized types generally less likely to be dissolved and transported. An environment with a range of oxidation states can provide a battery-like energy gradient exploitable by some types of microbes.

Opportunity’s Mystery

As Curiosity explores “Vera Rubin Ridge”, half a world away, NASA’s Mars Exploration Rover (MER) Opportunity has reached 5,000 Sols (Martian days) of operations on Mars in what was originally seen as a 90-day surface mission.

A view from the front Hazard Avoidance Camera on NASA’s Mars Exploration Rover Opportunity shows a pattern of rock stripes on the ground, a surprise to scientists on the rover team. It was taken in January 2018, as the rover neared Sol 5000 of what was planned as a 90-Sol mission. Credit: NASA/JPL

Currently, Opportunity is investigating a mystery of its own: a strange  ground texture resembling stone striping seen on some mountain slopes on Earth that result from repeated cycles of freezing and thawing of wet soil. The texture has been found within a channel dubbed “Perseverance Valley” the rover is exploring in an attempt to reach the floor of Endeavour crater. This 22 km (14 mi) diameter impact crater has been the focus of Opportunity’s studies since it reached the edge of the crater in October 2011.

The striping takes the form of soil and gravel particles appearing to be organised into narrow rows or corrugations, parallel to the slope, alternating between rows with more gravel and rows with less. One possible explanation for their formation is that on a scale of hundreds of thousands of years, Mars goes through cycles when the tilt, or obliquity, of its axis increases so much that some of the water now frozen at the poles vaporises into the atmosphere and then becomes snow or frost accumulating nearer the equator and around the rims of craters like Endeavour.

Continue reading “Space Sunday: Mars rover round-up”

Space Sunday: images of Mars, comets and giant planets

Looking across Gale Crater as it might appear from NASA’s Mars Science Laboratory rover Curiosity. Render created by Kevin M Gill.

Kevin M. Gill is a software engineer, planetary and climate data wrangler at NASA’s Jet Propulsion Laboratory. He’s been working with digital terrain models and ortho images from the HiRISE imaging system aboard NASA’s Mars  Reconnaissance Orbiter (MRO) to create some stunning computer models and images of Endeavour and Gale craters, where the Opportunity and Curiosity rovers are exploring, as well as other regions of Mars. These have caused a stir on social media this week, and rightly so.

Kevin provides a detailed description of how he produces the images, which involves a range of software tools including ImageMagick, Maya and Photoshop. For those interested in creating computer renderings, his post makes a fascinating read; for those who love images of Mars, his images offer a stunning new perspective on the planet. The images utilise a slight vertical height exaggeration and false colour / lighting adjusted to Earth daylight standards, but the results are undeniably stunning.

A view along a volcanic fissure in the Cerberus Palas region of Mars. Rendering by Kevin M. Gill

Some of the images offer a unique perspective on surface features, such as the one above, showing a volcanic fissure in Cerberus Palas in the north-eastern Elysium quadrangle of Mars.

For those interested in producing vistas of Mars in a platform such as Linden Lab’s Sansar, Kevin’s work and notes could offer a starting point. In turn, Sansar could offer the perfect VR visualisation platform for allowing people to “visit” and learn about Mars.

“Mount Sharp” (Aeolis Mons), the mound of material deposited against the central impact peak of Gale Crater. Render by Kevin M Gill.

Meanwhile, the MSL team are moving closer to resuming drilling operations with the Curiosity rover.

These were suspended in December 2016. Prior to that, Curiosity had used the drill system mounted on its robot arm a total of 15 times between 2013 and 2016. On each of those occasions, two contact post, one either side of the bit, were placed on the target rock before the bit was extended by the drill feed mechanism, helping to gauge and support the drill. It was reliability issues with the feed mechanism which led to the suspension of all drilling operations.

Engineers have been investigating ways to use the drill without any reliance on the feed mechanism. This requires the drill to remain extended, the rover’s arm bringing it directly in contact with the rock to be drilled, without any support from the stabilising arms. In order for this to work, it is essential the drill bit  – which not only cuts into rocks, but gathers samples from within them – can be placed with minimal downward or side-to-side pressure or motion on it, to ensure it is not damaged or becomes stuck.

The issue here is that when supported by the stabilisers, the drill had only one axis of movement, without them, it could be subject to fix degree freedom of movement as vibrations from the drilling process feed back into the rover’s arm. To minimise this risk, tests are being carried out to determine if sensors in the robot arm are sensitive enough to detect potentially damaging motions in the drill when in use, and shut down the drilling operation.

On October 17th, 2017, NASA conducted the first test with Curiosity’s robot arm aimed at resuming the rover’s ability to gather rock samples with the drill mounted on the arm. Credit: NASA/JPL

To this end, on October 17th, 2017, Curiosity was commanded to place the drill bit in contact with a rock for the first time in ten months and without the use of the stabilisers. The bit was then gently pressed downward and moved slightly from side-to-side to see how well the sensors responded, the idea being that when the drill resumes operations, the sensors can be used to automatically detect potentially harmful movements in the drill head which could result in the bit being damage or becoming stuck.

It’s still likely to be several months before Curiosity resumes drilling operations, with further tests in the planning. However, mission managers are optimistic the rover will at some point be able to resume use the drill to gather samples from within rocks for analysis.

Deep Space Gateway Gains Momentum

On November 1st, 2017, NASA awarded contracts to five companies to examine how they can develop a power and propulsion module as the initial element of the agency’s proposed Deep Space Gateway.

As currently envisioned, the power and propulsion module will generate electrical power for the gateway, provide a communications relay and use a solar electric engine for manoeuvring the station in cislunar space. NASA had been examining their own ideas for the module, but it is hoped that the contracts will allow industry the chance to present their own ideas and technologies in support of the module’s development.

Part of the NASA studies involve the use of a 50-kilowatt solar electric propulsion (SEP) motor for the module, the idea being that if successful, the system could be scaled-up for use on missions to Mars.  While SEP systems can’t generate much thrust, they can run for long periods and are far more efficient than chemical systems.

Artist’s concept of the Deep Space Gateway passing close to the Moon. Credit: NASA

NASA had planned to test the SEP concept on the robotic portion of the now-cancelled Asteroid Redirect Mission (ARM), in which a robotic spacecraft would obtain a boulder-sized sample of a near Earth asteroid and return it to cislunar space for examination by astronauts. With the cancellation of that mission, the SEP programme has been in limbo; so issuing the contracts might both help revive the SEP project and allow commercial organisations weigh-in on the work.

These contracts are separate from those issued in 2016 to examine development of habitat modules for the gateway. However, all five of the companies that received contracts for Power and Propulsion Element studies also either have a habitat award or are partnered with a company that does.

How NASA plans to proceed with development of the station, including how it procures it from industry, will depend on the outcome of the studies as well as NASA’s overall exploration planning. At this point in time – and despite the October 5th, 2017 directive from the inaugural meeting of the re-invoked US National Space Council (NSC) concerning an American return to the Moon – the Deep Space Gateway remains a concept, not a formal NASA programme.

Also interested in participating in the programme is the European Space Agency. They are hoping to have a dedicated module forming part of the station, and are offering to develop a resupply system potentially capable of delivering up to nine tonnes of supplies to the Gateway.

The resupply vehicle would likely use the Ariane 6 launcher and solar electric propulsion system, rated around 60 kilowatts. ESA representatives believe the system could be ready for operation in 2025 or 2026, which fits with the time frame for the station’s development – which could see the power and propulsion module launched in 2022, as part of NASA’s Exploration Mission 2 mission for the Orion / Space Launch System. In the meantime, the first launch of the Ariane 6 booster is currently scheduled for 2020.

Continue reading “Space Sunday: images of Mars, comets and giant planets”