Dunes, rocks, comets and dust

CuriosityThe progress of NASA’s Curiosity rover on Mars has slowed somewhat in January, the rover having covered around 265 metres (865 feet) in the month, bringing the total distance Curiosity has travelled since arriving on Mars in august 2012 to some 4.89 kilometres (3.04 miles).

Part of the reason for the slow-down has been due to the recent traverse of considerably rougher terrain during the rover’s trek towards its encounter with “Mount Sharp” having resulted in somewhat more wear-and-tear of the aluminium wheels than had perhaps been anticipated.

While not of a serious concern – the rover can function with quite substantial damage having being done to the wheels – the mission team has nevertheless been looking for ways and means for the rover’s progress to continue at a reasonable pace, but without exposing the wheels to excessively rugged terrain.

Most recently, this has involved examining a possible gateway to a smoother route down to the point at which they plan to commence explorations of “Mount Sharp’s” lower slopes.  This gateway is a 1-metre (3-ft) high sand dune sitting between two rocky scarps. Dubbed “Dingo Gap”, the dune appears to provide access to a smoother route heading south-west and towards the rover’s ultimate destination.

Dingo Gap, imaged on Sol 526 (January 28th, 2014). Taken by the “left eye” of Curiosity’s Mastcam, this mosaic shows the metre high dune in the upper centre of the picture, sitting between two rocky scarps and about 35 metres (115 ft) from the rover. The far horizon of the image is the wall of Gale Crater (click to enlarge)

“The decision hasn’t been made yet, but it is prudent to go check,” said Jim Erickson, NASA’s project manager for Curiosity. on January 28th. “We’ll take a peek over the dune into the valley immediately to the west to see whether the terrain looks as good as the analysis of orbital images implies.” The orbital images he referred to came from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter, while the “closer look” actually took place on January 30th.

In addition to using alternative routes, the drive team has also been evaluating possible driving techniques that might help reduce the rate of wheel punctures, such as driving backwards or using four-wheel drive instead of six-wheel drive. This may help is situations where some of the wheel damage may have resulted from the force of the rear wheels pushing the middle or front wheels against sharp rocks, rather than simply the weight of the rover driving over the rocks.

As a result of the slow-down, JPL are considering introducing some evening and weekend drives into the February drive schedule.

A mosaic showing Dingo Gap (foreground) and the terrain beyond, as imaged by Curiosity’s monochrome Navcams on Sol 528 (January 30th, 2014) – click to enlarge

More Drilling

As well as providing a route southwards, Dingo Gap may also allow the rover easier access to its next waypoint on the journey, where it is expected to carry out further drilling and sample-gathering activities. The site, identified as “KMS-9” is around 800 metres (half-a-mile) from Curiosity’s current position when measured in a straight line – but that is over rugged terrain the mission team would potentially avoid if possible.

The drilling site has been imaged from orbit, and holds significant appeal to the mission team, as Katie Stack, a science team collaborator explained. “At KMS-9, we see three terrain types exposed and a relatively dust-free surface. This area is appealing because we can see terrain units unlike any that Curiosity has visited so far. One unit has striations all oriented in a similar direction. Another is smooth, without striations. We don’t know yet what they are. The big draw is exploration and seeing new things.”

“KMS-9” won’t be the first rocky area examined by Curiosity in 2014. On January 15th, the rover examined a rock dubbed “Harrison”, which revealed linear crystals with feldspar-rich composition.

Earth-side Tests

At the same time as the efforts to select a candidate route have been underway, other members of the team have been carrying out further tests to validate capabilities for the rover to drill for rock samples on the kind of slopes it will likely encounter when exploring and climbing “Mount Sharp”.

In particular, the tests have been focused on the drill mechanism’s ability to withstand damage as a result of slippage when the rover is parked on a sloping surface. So far, results have shown that the drill mechanism can withstand slippage of around 5 centimetres (2 inches) in the rover’s position without any real damage occurring. Such slippage could be induced through a number of circumstances, including the angle of slope, cumulative damage to the wheels which may impact their ability to grip the surface beneath them, and material on the surface which may also impact the rover’s ability to sustain a solid grip on underlying rock.

Cometary Close-up

In October 2014, Curiosity, together with Opportunity and craft in orbit about the planet could be in for what NASA is calling a “barnstorming” show, as comet C/2013 A1 Siding Spring makes a close pass on the planet at a distance of about 130,000 kilometres (86,000 miles) – around 10 times closer than any identified comet has passed by Earth.

Comet Siding spring’s forthcoming encounter with Mars in October 2014

Given the distance between the comet and the planet, it is hoped that orbiting spacecraft could get a good look at the comet’s nucleus as it slingshots its way back out of the solar system. However, the encounter is not without risk. As a comet approaches the Sun, it becomes more volatile as radiation heats it and causes material to “boil off” of the rocky nucleus, giving rise to the majestic-looking tail. This ever-spreading plume of fast-moving dust presents a real risk to vehicles in orbit around Mars. Already images captured on the comet earlier in January 2014 show it to be very active, but it’s going to be another few months before scientists know precisely how active, and what danger the dust will actually present to vehicles orbiting Mars.

“Our plans for using spacecraft at Mars to observe comet Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do that,” said Rich Zurek, Mars Exploration Program chief scientist at JPL when discussing the encounter.

This won’t be the first time vehicles orbiting Mars have been used to examine comets. In 2013, researchers were able to observe comet ISON (formally C/2012 S1) as it passed by Mars at a distance some 80 times greater than of comet Siding Spring’s passby.

ISON eventually carried on into the solar system and eventually disintegrated as it passed too close to the Sun. Siding Spring – name after the Australian observatory which first identified it on January 3rd, 2013 – won’t share the same fate. By the time it passes Mars on October 19th, 2014, it will already be effectively heading back out into deep space, have reached the point of its closest approach to the Sun some six days before its encounter with the Red Planet. It won’t be making any return for about a million years.

Siding Spring as seen by NASA’s NEOWISE on January 16, 2014. Despite being 571 million kilometres (355 million miles) from the Sun, the comet is already very active

Scientists are particularly interested in any interaction material from the comet’s tail has with the Martian atmosphere. If the tail is particularly large and active, it is expected that both Curiosity and Opportunity will witness a significant number of daytime meteors. It’s also thought that infalling dust particles could heat-up the upper reaches of the tenuous Martian atmosphere and expand it, causing something similar to the spring warming of the atmosphere which takes place and can lead to dust storms on the planet. Operating from orbit, both the Mars Reconnaissance Orbiter (MRO) and Mars Odyssey, together with Europe’s Mars Express will be monitoring the Martian atmosphere with infrared sensors to see if this is the case, while Mars Express and the MRO will attempt to image the comet with their high-resolution cameras.

Opportunity: Ten Years On

In my last MSL report, I covered the tenth anniversary of Mars Exploration Rover Opportunity’s arrival on Mars. Since then, NASA has released a number of commemorative videos. Here the Mission’s Principal Investigator, Steve Squyres, and mission scientist Matt Golombek discuss the science aspects of the mission.

MSL mission reports in this blog

video and images courtesy of NASA JPL