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.
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 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.
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.
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.