Tag Archives: MSL

Of mountains, methane and molecules

CuriosityAfter what has been a relatively quiet period in terms of news from Mars, things are once again proving interesting.

The first uptick came following the start-of-month teleconference Mars Science Laboratory personnel held to summarise the results of the last several months of activities the Curiosity rover has been performing in Gale Crater. In particular, these have allowed scientists to better determine how the 5 kilometre high mound at the centre of the crater may have been formed.

Even before Curiosity arrived on Mars, sufficient evidence had been obtained from orbit to show that features in and round Gale Crater were likely influenced by water-related activity. Curiosity itself found evidence for water once having flowed freely across parts of the crater when it encountered the beds of ancient rivers and streams as it explored the regions dubbed “Glenelg” and “Yellowknife Bay”.

With the journey down to “Mount Sharp”, and NASA call the mound, and the recent explorations of its lower slopes, the science team have been able to piece together the processes that led to its formation.

The first clues came while Curiosity was still en route to the point where examination of the “Mount Sharp’s” lower slopes could begin. As it drove southwards and towards the mound, the rover started to encounter layered sandstone deltas, all inclined towards “Mount Sharp”. On Earth, such layered, angled deposits are found where a river flows into a large lake.

A mosaic of images captured by Curiosity’s Mastcam on March 13, 2014 PDT (Sol 569). White-balanced for natural Earth light, the images show layered sandstone deposits, all pointing towards “Mount Sharp”, indicative of delta sediments dropped by a flowing river as it enters a large lake

Once in the foothills of “Mount Sharp”, in the area dubbed “Pahrump Hills”, Curiosity has repeatedly come across layers of tightly-compacted sedimentary mudstone which are entirely consistent with the sedimentary layering found in the muds and rock in lake beds on Earth. Intriguingly, while most of these layers appear to have been formed by sediments settling out of a large, still body of water, some of them appear to have been affected by wind erosion.

This latter point would indicate that rather than the crater floor once being covered by a single body of water which gradually vanished over time, it was subjected to cycles of wet and dry periods, giving rise to a number of lakes forming within the crater over the ages, each one only a few metres deep. As the water receded / vanished during the dry periods, so the uppermost layers of each lake bed were exposed to the wind, eroding them, before the next wet period started, and a new lake formed, gradually depositing more sediments on top of them.

Thus over a period of millions of years, Gale Crater was home to numerous lakes, each of them fed by assorted rivers and streams flowing into them, giving rise to the alluvial plains around the base of the crater walls, and the sedimentary deltas closer to “Mount Sharp” where these rivers and streams met the standing waters of each lake.

This diagram depicts a vertical cross section through geological layers deposited by rivers, deltas and lakes. A delta builds where a river enters a body of still water, such as a lake, and the current decelerates abruptly so sediment delivered by the river settles to the floor.

This view of Gale Crater is further supported by measurements of the deuterium-to-hydrogen ratio in the rocks sampled by Curiosity. These suggest that the sediments the rover is now examining were laid down during a period when Mars had already started losing its surface water, suggesting an extended period of climatic change on the planet, where the amount of free-standing water may well have been in flux.

Once the water had completely vanished from Gale Crater, it seems likely that “Mount Sharp” was sculpted by wind action within the crater. Thus, it is thought, would have eroded the material of the alluvial plains faster than the more densely compacted mudstone formed under the weight of the successive lakes.

As it might have been: the left image shows the repeated depositing of alluvial and wind-blown matter (light brown) around a series of central lakes which formed in Gale Crater, where material was deposited by water and more heavily compressed due the weight of successive lakes (dark brown). Right: once the water had fully receded / vanished from the crater, wind action took hold, eroding the original alluvial / windblown deposits around the “dry” perimeter of the crater more rapidly than the densely compacted mudstone layers of the successive lake beds, thus forming “Mount Sharp”

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Of Martian walkabouts, pictures from a comet, and getting ready to fly

CuriosityIn my last report on the Mars Science Laboratory, I mentioned that Curiosity has been on a geology “walkabout” up the slopes of the “Pahrump Hills” at the base of “Mount Sharp” (more correctly, Aeolis Mons). The zigzagging route up through the area took the rover from “Confidence Hills” and the location of the last drilling operation up to a point dubbed “Whale Rock”, the drive being used to gather information on potential points of interest for further detailed examination.

The exposed rocks in this transitional layering between the floor of Gale Crater, in which Curiosity arrived back in August 2012, and the higher slopes of “Mount Sharp” is expected to hold evidence about dramatic changes in the environmental evolution of Mars. Thus, the “walkabout”  – a common practice in field geology on Earth – was seen as the best means of carrying out a reasonable analysis of the area in order for the rover to be most efficiently targeted at specific locations of interest.

Curiosity’s walkabout, from “Confidence Hills” to “Whale Rock” in October, the rover is now working its way back to various points of interest for further studies

“We’ve seen a diversity of textures in this outcrop,” Curiosity’s deputy scientist Ashwin Vasavada (JPL) said of the drive. “Some parts finely layered and fine-grained, others more blocky with erosion-resistant ledges. Overlaid on that structure are compositional variations. Some of those variations were detected with our spectrometer. Others show themselves as apparent differences in cementation or as mineral veins. There’s a lot to study here.”

During the drive, Curiosity travelled some 110 metres, with an elevation of about 9 metres, using the Mastcam and the ChemCam (Chemistry and Camera) laser spectrometer system to inspect and test potential points of interest for more detailed examination at a later date. Since completing that drive, the rover has been working its way back through Pahrump Hills, this time examining specific targets using the robot-arm mounted Mars Hand Lens Imager (MAHLI) camera and spectrometer. Once this work has been completed, specific targets for in-depth analysis, including drilling for samples will for the core activity of a third pass through the area.

So far, two specific areas have been identified for detailed examination. The first, dubbed “Pelona” is a  fine-grained, finely layered rock close to the “Confidence Hills” drilling location. The second is a small erosion-resistant ridge dubbed “Pink Cliffs” the rover drove around on its way up the incline.

“Pink Cliffs” is roughly a metre (3ft) in length and appears to resist wind erosion more than the flatter plates around it.As such, it offers precisely the kind of mixed rock characteristics mission scientists want to investigate in order to better understand “Mount Sharp’s” composition. This image is a mosaic of 3 pictures captured on October 7th PDT, 2014 (Sol 771 for the rover) by Curiosity’s Mastcam. It has been white balanced to show the scene under normal Earth daylight lighting – click for full size.

Another target of investigation has been the edge of a series of sand and dust dunes right on the edge of “Pahrump Hills”.  In August 2014, Curiosity attempted to use these dunes as a means to more quickly access the “Pahrump Hills” area, but the effort had to be abandoned when it proved far harder for the rover to maintain traction than had been anticipated, particularly given the rover has successfully negotiated sandy dunes and ridges earlier in the mission. As a result, scientists are keep to understand more about the composition of the dunes.

On November 7th, Curiosity was ordered to venture onto the dunes very briefly in order to break the surface of one of the rippled dunes and expose the underlying layers of sand in an effort to better understand why the rover found the sand such hard going the first time around, and what might be within these wind-formed dunes that would prove to be so bothersome to driving over them. Data gathered from the drive is still being analysed.

Spanning roughly 1.2 metres from left to right, a wheel track breaks the surface of a dust sand dune ripple on the edge of “Pahrump Hiils”. The MSL science team hope the exposed material within the ripple will help them understand why Curiosity found these dunes hard-going when trying to cross them in August 2014.

The work in the “Pahrump Hills” area has given rise to concerns over one of the two lasers in the ChemCam instrument. As well as the main laser, known for “zapping” targets on the surface of Mars in order to reveal their chemical and mineral composition, the system uses a second laser, a continuous wave laser, used for focusing the ChemCam’s telescope to ensure the plasma flash of vaporised rock is properly imaged when the main laser fires. Data received on Earth when using the ChemCam to examine rocks on the first pass through “Pahrump Hills” suggests this smaller laser is weakening and may no longer be able to perform adequately.

If this is the case, the laser team plan to switch to using an auto-focus capability with the telescope so it will automatically focus itself on a few “targeting” shots from the main laser ahead of any data-gathering burst of fire, allowing for proper telescope calibration.

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Of triumph and tragedy

The last week has seen some momentous and tragic events occur in the annals of space flight and space exploration, with tragedy leading the way following the break-up of Virgin Galactic’s SpaceShipTwo vehicle on Friday, October 31st, resulting in the death of co-pilot Michael Alsbury and the serious injury of pilot Peter Siebold.

The loss of SpaceShipTwo came just a few days after an Antares booster, operated by Orbital Sciences and which should have been launching an unmanned Cygnus resupply vehicle to the International Space Station (ISS), was ordered to self-destruct seconds after lifting off of the pad.

Understandably overshadowed by the loss of SpaceShipTwo was the news that China has enjoyed a further success as a part of its ambitious lunar mission plans, and NASA has achieved a further “first” on Mars with Curiosity.

The news from Curiosity came after what has been another period of relative quiet from the MSL team following the successful gathering of a rock sample from a drilling operation into a target rock outcrop dubbed “Confidence Hills” within the “Pahrump Hills” region at the base of “Mount Sharp”.

Since that time, Curiosity has been on something of a “walkabout”, as NASA JPL is calling it (“roll around” probably doesn’t give the right impression…) within the “Pahrump Hills” area whilst simultaneously analysing the samples gathered from “Confidence Hills” at the end of September, and also keeping an eye out for passing comets.

Curiosity’s “walkabout” in the “Pahrump Hills” at the base of “Mount Sharp” in October 2014. The route starts at “Confidence Hills”, the site of a successful drilling operation, and winds up to “Whale Rock”. Red dots indicate points at which the rover paused overnight, white dots denote points at which it stopped to gather images and data, perhaps over several days

As well as the familiar aboriginal reference, “walkabout” is also a term used by field geologists to describe walking across a rocky outcrop in order to determine the best places from which to examine it – which is precisely what Curiosity was ordered to do through October.

During the walkabout, Curiosity made a number of stops for data and image gathering, before arriving at a point dubbed “Whale Rock”, just below another high point which appears to mark the point at which “Pahrump Hills” join the “Murray formation”, the next destination for the rover once studies of “Pahrump Hills” has been completed. The rover will remain parked at “Whale Rock” as the science team analyses the images and data gathered in order to determine where the rover should return to carry out more detailed investigations.

The material obtained from the “Confidence Hills” drilling operation contained in the rover’s sample scoop after being sifted and graduated by the CHIMRA device in the rover’s robot arm turret, and about to be delivered to the input ports ready for analysis by the instruments in the rover’s body. This image was taken by Curiosity’s Mastcam, and has been white-balanced so that lighting conditions match daytime light on Earth

In the meantime, and in the “first” mentioned above, Curiosity has confirmed that the samples gathered from “Confidence Hills” contain mineral deposits what had been mapped from orbit. The mineral in question in Hematite – which has been found elsewhere on Mars by both of the MER rovers, Opportunity, and the now defunct Spirit.

However, the significance of the “Confidence Hills” analysis, carried out by the rover’s on-board Chemistry and Mineralogy (ChemMin) instrument, confirms predictions made from the analysis of data returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter that Hematite deposits would exist within the rocks of the mountain’s lower slopes. This confirmation gives the science team greater confidence that the analysis of orbital data can help them make even better choices of while the rover should carry out drilling operations etc. It also means that the rover’s on-the-spot analysis and observations can be set directly into the broader geologic history of “Mount Sharp” as obtained by orbital data.

Curiosity may spend weeks or months at Pahrump Hills before proceeding farther up into the “Murray formation” and on to “Hematite Ridge”, a further location of interest to scientists. The mineral is of particular interest to scientists not so much because it might be indicative of a water-rich history in the region (as was the case with the discoveries made by Opportunity and Spirit) – Gale Crater has already more than yielded enough evidence of wet conditions being prevalent in its past history. Rather, the hematite on and in “Mount Sharp” helps scientists further understand oxidation conditions within the region. Continue reading

Duck and Cover

Sunday October 19th marked the culmination of what is regarded as one of the most unique astronomical events to take place in human history – so unique, some commentators believe it may only happen once every million years or so: the opportunity to study something which may have existed before the Earth was created.

For the last several months, comet Siding Spring has been under observation as it hurtles through the solar system at an acute angle relative to the plane of the ecliptic – the imaginary line along which the planets orbit, and on Sunday October 19th, it made its closest approach to Mars, passing just in front of the planet relative to the Sun.

Siding Spring was first identified by Australian astronomer Rob McNaught, and bears the name of his observatory as a result, although officially it is catalogued as C/2013 A1. Since then, it has been under observation from a veritable armada of international space craft, and its passage past Mars presents further unique opportunities for observation and data-gathering.

Siding spring is a comet originating in the Oort cloud, and beleived to be making perhaps its first foray into the inner solar system, passing inside the orbit of Jupiter

Siding spring is a comet originating in the Oort cloud, and believed to be making perhaps its first foray into the inner solar system, passing inside the orbit of Jupiter

The comet has been identified as coming from the Oort cloud (or the Öpik–Oort cloud, to give proper recognition both astronomers who initially and independently postulated its existence). This is a spherical cloud of debris left-over from the creation of the solar system, occupying a huge area starting some 2,000-5,000 AU (2,000 to 5,000 times the distance from the Earth to the Sun) and extending out to around 50-100,000 AU – or about one light year away. Thus, Siding Spring represents some of the material “left-over” from the formation of the solar system 4.6 billion years ago – older than the Earth itself. In fact, such is the distance of the Oort cloud from the Sun, that some postulate the much of the material within it may actually come from stars which shared the same “stellar nursery” as the Sun.

There is nothing unique per se about comets coming from the Oort cloud – it is one of two places from which all comets originate, the other being the Kuiper belt (or Edgeworth–Kuiper belt, as it is also known in recognition of the two astronomers to postulate its existence in the form we now know it has). A disk of material also from the early history of the solar system, the Kuiper belt orbits the Sun at a distance of around 30-50 AU, and gives rise to “periodic” comets. These are comets which circle the Sun in periods of up to 200 years. Two of the most famous Kuiper belt comets are comet Halley, with it 76-year orbit, and comet Shoemaker-Levy 9, which broke-up during a close approach to Jupiter in 1992 prior to colliding with the gas giant in 1994.

Siding Springs passage through the solar system

Siding Springs passage through the solar system

What makes Siding Spring of interest to astronomers is that this is probably the first time in its long, cold history it has ever come inside the orbit of Jupiter since it was first nudged out of the Oort cloud. This led Dr Michael Brown, an astronomer at Monash University, to describe the comet as “essentially a refrigerator of pristine parts of the creation of the solar system. The particles it gives off are effectively opening up the door of the fridge so we can see what the solar system was like 4.6 billion years ago.”

John Grunsfeld, former astronaut and associate administrator for NASA’s Science Mission Directorate in Washington was equally enthused by the comet’s passage, referring to it as “a cosmic science gift that could potentially keep on giving.” Speaking at a press conference held earlier in the year to discuss NASA’s plans to observe Siding Spring, he continued, “The agency’s diverse science missions will be in full receive mode.” He went on, “This particular comet has never before entered the inner solar system, so it will provide a fresh source of clues to our solar system’s earliest days.”

The chance for scientific discovery notwithstanding, the comet’s path was initially a cause for concern, at least in terms of Mars’ future. Early attempts to track the comet’s likely route  “up” through the solar system suggested that rather than passing the Red Planet, Siding Spring would in fact smash into it.

Had the comet struck, estimates suggest it would have created a crater between 10 and 15km in diameter, depending on the actual size of the comet’s nucleus, thought to be between 700m and 1km across.  While that is certainly enough to result in quite an extraordinary bang and some severe changes in the Martian atmosphere (not to mention the sizable dent it would make in the planet’s surface), Mars has actually withstood much larger impacts in its time.

Take Hellas Basin, for example. It is the largest visible crater in the solar system, some 2,300km (1,440 miles) across, and with an ejecta ring some 7,000km (4,375 miles) across. It is believed to have been created by the impact of an asteroid some 400km (250 miles) in diameter.

The Hellas Basin, shown in purple in the image of the right, above. Deeper than Mount Everest is tall, the depression was likely caused by the impact of an asteroid some 400km across. The impact also resulted in the Tharsis Bulge on the opposite side of the planet, and shown in red in the image on the left, topped by the three massive Tharsis volcanoes, and split by the 5,000km length of the Vallis Marineris

The Hellas Basin, shown in purple in the image of the right, above. Deeper than Mount Everest is tall, the depression was likely caused by the impact of an asteroid some 400km across. The impact also resulted in the Tharsis Bulge on the opposite side of the planet, and shown in red in the image on the left, topped by the three massive Tharsis volcanoes, and split by the 5,000km length of the Vallis Marineris

As Grunsfeld noted, such is the scientific opportunity presented by the comet, that NASA has put a significant number of assets in the front line of tracking and observing Siding Spring. These include the Hubble Space Telescope, the Spitzer infra-red space telescope, the WISE infra-red space telescope, the Chandra X-ray observatory, the Kepler orbital observatory (used in the search for Earth-sized extra-solar planets) and more, as well a host of ground-based observatories.

Foremost in the front line, by dint of the comet’s close passage past Mars, are NASA’s orbital and surface vehicles there. Curiosity, Opportunity, the Mars Reconnaissance Orbiter (MRO), Mars Odyssey and MAVEN, together with Europe’s Mars Express and India’s MOM, are all watching the comet, although for the orbiting spacecraft, this comes with a degree of risk.

Siding Spring has been, and is, under observation by an armada of science probes and also from observatories on Earth

Siding Spring has been, and is, under observation by an armada of science probes and also from observatories on Earth – including these from NASA

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