Tag Archives: MSL

Space Sunday: hill climbing, the impact of salt, and landing a rocket (take 2)

CuriosityApril 16th, 2015 saw NASA’s Mars Science Laboratory rover Curiosity clock-up 10 kilometres (6.25 miles) on its odometer since it arrived on Mars 30 months ago, as it continues its trek up the slopes of “Mount Sharp”, the mountain-size mound at the centre of Gale Crater.

The rover is currently making its way through a series of connected shallow “valleys” on the slops of the mound – which is more correct names Aeolis Mons – as it continues upwards and away from the “Pahrump Hills” area it spent 6 months investigating, and towards its next major science target, an area the science team have dubbed “Logan Pass”, which is still some 200 metres away from the rover at the time of writing.

While only a distance of around 550 metres separates “Logan Pass” from the upper limits of “Pahrump Hills”, the rover’s gentle progress has been the result of several stops along the way in order to further characterise the different rock types Curiosity has been encountering, and to make important observations of its surroundings as the science team try to understand the processes by which the region’s ancient environment evolved from lakes and rivers into much drier conditions.

A panoramic mosaic taken by Curiosity’s Navigation Camera (Navcam) on Sol 951 of the rover’s mission (April 10th, 2015, PDT). The view shows the terrain ahead of the rover within “Artist’s Drive”, the first of the shallow “valleys” the rover is traversing en route to the next point of scientific interest, “Logan Pass”

The rover’s progress up “Mount Sharp” has so far been through the lower reaches of the transitional layers which mark the separation points between the materials deposited over the aeons to create the gigantic mound and the material considered to be common to the crater floor. These transitional layers have been dubbed the “Murray Formation”, in honour of the late co-founder of The Planetary Society, Bruce Murray, and comprise a number of different land formations, “Pahrump Hills” being one of the lowermost. Logan Pass marks the start of another, dubbed the “Washboard unit”, and which comprises a series of high-standing buttes.

The lower slopes of “Mount Sharp” and the transitional nature of the “Murray Formation” between the create floor (left) and the “proper” slopes of the mound, marked by the “Hematite Ridge” (right). currently, the rover is now approach the lower extreme of a range of buttes within the “Murray Formation” which include “Murray Buttes” shown in the image. and which have been marked as a future science destination for Curiosity

As several of the MSL reports in these pages have shown, Curiosity has already found considerable evidence that Gale Crater may once have been home to environments sufficiently benign to allow for the existence of microbial life. Whether or not those microbes survived down the millennia such that they are still present in the planet’s soil today, is not something the rover is equipped to determine; however, a recent report from one of Curiosity’s science teams  suggests that subsurface conditions are unfavourable to the support of microbial life.

The evidence for this comes in the form of perchlorate salts, and the effect they can have on their environment. Perchlorate was first detected in soil samples gathered by NASA’s Phoenix Mars Lander mission in 2008, while Curiosity found trace evidence for perchlorate in samples gathered early in its own mission.

What makes perchlorate interesting is that in cold temperatures, it is able to “pull” water vapour from the atmosphere and bind with it, lowering its temperature, potentially allowing it to form sub-surface brines which would be very destructive to microbial life.

It had been thought that the environmental conditions by which this might occur were limited to the near-polar regions of the planet. However, data gathered by Curiosity’s on-board weather station, called REMS (for Rover Environmental Monitoring Station) over the course of its mission suggests the night-time conditions in Gale Crater, are right for the formation of sub-surface brines throughout the year.

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Space Sunday: ice-cream sandwiches, sniffing the air and targets of Opportunity

CuriosityCuriosity is continuing its exploration and ascent of “Mount Sharp”, the huge mountain-like mound of deposited material occupying the centre of Gale Crater, which has been the rover’s home since it arrived on Mars in August 2012. And it is continuing to find curious and enigmatic hints about the past conditions in the crater, and about Mars as a whole.

The rover’s most recent discoveries come from an area of rock dubbed “Garden City”, which contains areas of two-tone mineral veins quite unlike anything so far encountered in the rover’s travels.

The veins appear as a network of ridges left standing above the now eroded-away bedrock in which they formed. Individual ridges range up to about  6 centimetres (2.5 inches) high and half that in width, and they bear both bright and dark material. They are strongly suggestive of multiple episodes of fluid movement which occurred much later than the wet environmental conditions that formed lake-bed deposits which gave rise to “Mount Sharp’s” formation.

“Some of [the veins] look like ice-cream sandwiches: dark on both edges and white in the middle,” said Linda Kah, a Curiosity science-team member at the University of Tennessee, Knoxville. “These materials tell us about secondary fluids that were transported through the region after the host rock formed.”

This view from Curiosity’s Mast Camera (Mastcam) is a mosaic of 28 images showing a network of two-tone mineral veins standing up to a height of 6 centimetres (2.5 inches) from the surface of a rock dubbed “Garden City” – click for full size

On Earth, veins of this kind form as a result of fluids moving through move through cracked rock, depositing minerals in the fractures which often affect the chemistry of the surrounding rock. Curiosity has found bright veins composed of calcium sulfate visible on the surface of rocks at several other locations, which appears to be the same with the lighter material found as “Garden City”,   but the dark material suggest something else.

“At least two secondary fluids have left evidence here,” Kah said. “We want to understand the chemistry of the different fluids that were here and the sequence of events. How have later fluids affected the host rock?”

While there are no plans to gather any samples form “Garden City”, analysis of the three sets of samples gathered from within “Pahrump Hills” reveal that mineral deposits within the area vary according to elevation, revealing a complex process may have been responsible for the formation of the area. Samples taken from the lowest elevation of the area revealed themselves to be rich in clays and hematite, both of which commonly form under wet conditions.

However, at just a 5 metre higher elevation, jarosite, an oxidized mineral containing iron and sulfur that forms in acidic conditions, was the dominant mineral, while towards the top of the area, at an elevation of 10 metres, clay minerals and hematite were almost non-existent, and traces of jarosite were greatly reduced, while the samples – from “Telegraph Peak” – were rich in cristobalite and quartz, both of which are mineral forms of silica.

Quite what the process may have been that gave rise to this spread of deposits is unclear – the science team have several options to choose from, and are continuing their investigation.

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Space Sunday: nitrogen nibbles

CuriosityCuriosity, the Mars Science Laboratory rover, resumed operations on Mars resumed operations on March 11th 2015, after an electrical short circuit in the rover’s robot arm caused a suspension of activities while the matter was investigated, and short itself having triggered the rover to switch to a “safe” mode to prevent any potential damage.

The short, was not enough to damage the rover’s electrical systems in any way, occurred occurred when the was attempting to transfer samples of material gathered from a rock dubbed “Telegraph Peak” from the drill head to the CHIMRA system by subjecting the entire turret to rapid vibrations from the drills percussion action. Extensive tests were carried out over 10 days to try to determine if the short was transient, or indicative of a potential fault. Only one test during this time caused a further short, which lasted around 1/100th of the second, and didn’t interrupt the drill motor.

The results of the tests gave engineers a high degree of confidence that the short wasn’t indicative of the major fault developing, and so operations recommenced on March 11th with the transfer of some of the “Telegraph Peak” material being delivered to the rover’s on-board laboratory while analysis of the results from the tests carried out on the drill mechanism continue to be examined.

Walkabout and onwards drive: an overlay showing Curiosity’s meanderings through the “Pahrump Hills” area at the base of “Mount Sharp” from September 2014 through March 2015. The rover is now proceeding further upwards along the slopes of “Mount Sharp”, and will use the valley dubbed “Artist’s Drive” to reach its next destination

As Curiosity now heads on up the slopes of “Mount Sharp”, aiming to pass through a shallow valley dubbed “Artist’s Drive”, NASA  has confirmed that the rover has found “biologically useful nitrogen” on Mars.

Nitrogen is essential for all known forms of life, since it is used in the building blocks of larger molecules like DNA and RNA, which encode the genetic instructions for life, and proteins, which are used to build structures like hair and nails, and to speed up or regulate chemical reactions. On Earth and Mars, however, atmospheric nitrogen is locked up as nitrogen gas (N2) – two atoms of nitrogen bound together so strongly that they do not react easily with other molecules; they have to become “fixed” (separated) in order to participate in the chemical reactions needed for life.

On Earth, certain organisms are capable of fixing atmospheric nitrogen and this process is critical for metabolic activity. However, smaller amounts of nitrogen can also be fixed by energetic events like lightning strikes.

An updated version of Curiosty's "selfie" from February 2013, when the rover was examining the rock dubbed "John Klein".  The original image rendered a "fishbowl" look; in this revised image, the background has been flatened and rendered as seen from a single point in the camera's field of view, while the view of Curiosity is made up of a number of images captured by the rover's Mars Hand Lens Imager (MAHLI)

An updated version of Curiosity’s “selfie” from February 2013, when the rover was examining the rock dubbed “John Klein”. The original image rendered a “fishbowl” look; in this revised image, the background has been flatenned and rendered as seen from a single point in the camera’s field of view, while the view of Curiosity is made up of a number of images captured by the rover’s Mars Hand Lens Imager (MAHLI) – image: NASA / JPL

While Nitrogen has long been known to exist on Mars, a study by the NASA team supporting the Sample Analysis at Mars (SAM) experiment onboard the rover reveals that NO3, a nitrogen atom bound to three oxygen atoms and a source of “fixed” nuitrogen  has been found in numerous samples gathered by the rover during its journey across Gale Crater.

Although the report’s authors make it clear that there is no evidence to suggest that the fixed nitrogen molecules they’ve discovered were created by life. The confirmation that NO3 does exist adds significant weight to the potential for Mars once having the kind of environment and building blocks needed by life. This is particularly relevant, given that one of the areas in which the NO3 was identified is the “Yellowknife Bay” area, which Curiosity examined in early 2013, and which was shown to have once had a very benign environment for life processes, complete with water, many of the right chemicals, and a local source of energy. This prompted Jennifer Stern of NASA’s Goddard Space Flight Centre in Greenbelt, Maryland, and a co-author f the report to note, “Had life been there, it would have been able to use this nitrogen.”

However, it is more likely that the fixed nitrogen that has been discovered may have been generated primarily by the numerous powerful impacts that occurred about 4 billion years ago, during a period known as the Late Heavy Bombardment, when the inner planets of the solar system were “hoovering up” the remaining debris of asteroids and rock scattered across their orbits.  That said, “fixed” nitrogen has also been detected high in the modern day Martian atmosphere by Europe’s Mars Express.  What’s missing at the moment is the capability to get a big enough nitrate signal for any nitrogen isotope data which might exist, as none of the experiments on Mars are broad enough to do so, thus this is likely to be something future missions to Mars will consider.

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Short circuits on Mars and mapping asteroids

CuriosityFollowing my last Curiosity update, which noted that other than for one potential drilling / sampling target, work was wrapping-up for the Mars Science Laboratory in the “Pahrump Hills” location on the lower slopes of “Mount Sharp”, the decision was taken to indeed gather one more sample.

The selected target had been dubbed “Telegraph Peak”, and sits towards the top end of “Pahrump Hills”. It was selected because Alpha Particle X-ray Spectrometer (APXS) measurements carried out by the rover during its 5-month “walkabout” in “Pahrump Hills” revealed the rocks in the area to be relatively enriched in silicon when compared to the corresponding amounts of aluminium and magnesium, which is somewhat different to rocks sample prior to the rover arrival at the basal slops of “Mount Sharp”. This enrichment has also shown to increase the further up the slopes of “Pahrump Hills” the rover climbed, which is of interest to the science team.

“When you graph the ratios of silica to magnesium and silica to aluminium, ‘Telegraph Peak’ is toward the end of the range we’ve seen,” Curiosity co-investigator Doug Ming explains. “It’s what you would expect if there has been some acidic leaching. We want to see what minerals are present where we found this chemistry.”

Sampling took place on February 24th, 2015 (PDT) or Sol 908 for the rover on Mars. For the first time in Curiosity’s time on Mars, it was carried out with no preliminary “mini-drill” operation. Instead, the science team judged that analysis of the rock by APXS indicted it was of a very similar nature to the previous two sample drilling sites in “Pahrump Hills”, and the new lower percussion drilling capabilities the rover now has were judged as sufficiently safe enough to go ahead with a direct sample gathering operation.

How the drill works: On the left, a view of the drill mechanism mounted on the rover's turret, with the drill bit centre bottom. On the right a cutaway showing the sample collection mechanism in the drill bit

How the drill works: On the left, a view of the drill mechanism mounted on the rover’s turret, with the drill bit centre bottom. On the right a cutaway showing the sample collection mechanism in the drill bit

As I’ve covered previously in these pages, obtaining a sample for analysis is a multi-part operation. First the rock is drilled, and a core sample forced up through the drill bit into a one of two sample collection chambers at the top of the drill mechanism. From here, the sample is “shaken” through a feed to another device in the rover’s robot arm turret called CHIMRA – the Collection and Handling for In-Situ Martian Rock Analysis system, used to separate the tailings through a series of sieves, ready for different sizes of sample grains to be passed through the the rover’s on-board laboratory systems.

Both of these operations require the use of the drill’s percussive system to vibrate the turret, forcing material both from the drill’s sample collection chamber and through CHIMRA. However, on February 27th, during the initial operation to move the sample tailings from the drill chamber to CHIMRA, Curiosity’s on-board fault protect system identified a transient short circuit within the robot arm’s electronics. The immediately resulted in all arm-related activities being shut down, and the arm and turret locked into position ready for diagnostic operations to commence.

A transient short can occur for a number of reasons, and can pass without significant problems. However, it may also indicate a potential issue which might require some measure of action, such as a change in operating procedures or a restriction on how a mechanism is used, in order to avoid the issue becoming a serious problem in the future. To this end, following the fault report, mission engineers started diagnosing the problem, with almost all rover operations halted while they did so.

A monochrome image from Curiosity’s Navigation Camera (Navcam) shows the position in which the rover held its arm for several days after a transient short circuit triggered on-board fault-protection programming to halt arm activities on February 27th, 2015 PDT, the 911th Sol of the rover’s work on Mars.

On Thursday, March 5th, as a part of the investigative process, the rover was commanded to carry out a series of vibration tests of the kind performed while forcing the transfer of samples from the drill to CHIMRA. The vibrations were carried out with the robot arm and turret in the same orientation and position which caused the initial triggering of the fault protection system, and in the third of 180 repeat motions, a similar transient short occurred, lasting less than one one-hundredth of a second, enough to trigger the rover’s fault protection systems, and confirming there does appear to be some kind of electrical issue.

Tests are now under-way to determine whether or not the short will occur with the turret in different orientations, and may be followed by additional tests to see if it occurs with the arm in different positions. If no shorting occurs with either a change in the orientation or position of the turret / arm, then the most obvious step in preventing any recurrence of the issue is to avoid placing the turret / arm in the same orientation for sample transfer operations during future drilling activities.

It is hoped that the tests can be completed in the course of the next week. If they show that operations can be resumed safely, it is anticipated that the sample transfer operations will be completed, and Curiosity will then be ready to resume its climb up “Mount Sharp”, leaving “Pahrump Hills” via a narrow valley the science team have dubbed “Artist’s Drive”.

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