Rovers on Mars continue to been busy as they trundle around the planet. While it has been there the longest, NASA’s Mars Science Laboratory (MSL) rover Curiosity has been somewhat out of the news, courtesy of it’s sister Perseverance and China’s Zhurong. However, it has recently re-grabbed the science news headlines thanks to a couple of studies.
Methane blips have pinged on Curiosity’s Tunable Laser Spectrometer (TLS) six times since the rover landed in Mars’ Gale crater in August 2012. These events have been seen as important, because methane is the by-product of two processes that share equal interest to scientists, because one is the result of organic processes – life – and the other, though inorganic in nature, points to geological activity closely tied to the presence of liquid water, a vital ingredient for past or present life as we know it to thrive.
A critical factor with methane is that once exposed to sunlight, it breaks down over a period of just 300-330 years, so for Curiosity to be able to detect it, it must have come from a relatively recent source – one that still may be active. The problem until now has been to locate that source – or even confirm Curiosity’s findings.
The best placed tools for doing the latter are aboard the European Space Agency’s Trace Gas Orbiter (TGO), but to date, TGO has been unable to detect any methane within Gale Crater. The could either be because there isn’t any methane to be found, or the minute amounts – just 10 parts per billion (10 ppb) – is too small and too localised for TGO to accurately detect from orbit, and Curiosity just happens to be sitting practically on top of it.
In one of two reports released in June, members of the MSL’s extended science team they have pin-pointed the source location for the methane, and that the rover happened to arrive in Gale Crater at a point extremely close to it.
This was done by treating each point of detection as a discrete packet of methane, then calculating the wind speed and direction at the time it was detected. This allowed them to trace the parcels back through time to their possible points of emission. By doing this for all of the different detection spikes, they were able to triangulate regions where the methane source is most likely located- and one of them is just a few tens of kilometres to the north-west of “Mount Sharp” and Curiosity’s area of exploration.
Sadly while tantalisingly close to the rover, the point is still well outside of Curiosity’s route of exploration.
A second study coming out of Curiosity’s science data suggests that a process has been at work on Mars that has been both eradicating evidence for possible past life on Mars – and creation conditions in which new life might arise.
In short, when reviewing the result of samples taken of ancient mudstone, a sedimentary rock containing clay, taken from two points just 400 metres apart and believed to have both been laid down some 3.5 billion years ago. Both should have been very similar in nature, rich in clay, an important element in the search for life, as it is both created in the presence of water and is an excellent medium for storing microbial fossils. However, one of the samples contained just half the anticipated amount of clay minerals in comparison to the other, but a much higher concentration of iron oxides – the compounds that give Mars its rusty hue.
The researchers behind this discovery believe it is the result of one of the two areas of mudstone being exposed to brine: salty water that leaked into the mineral-rich mudstone and effectively leached the clays and other minerals out of them, effectively eradicating both the geological and possibly the biological record that might otherwise be present in the deposits. Given that evidence of potentially brine-rich outflows have been found elsewhere on Mars, this study suggests this process might be common to regions of the planet believed to have once housed bodies of water, possibly destroying any evidence of past life.
However, the process – called diagenesis – is not all bad news. While it may well help erase any record of past organic activity from parts of the surface or Mars, it may also have triggered new life processes under the surface, the salty water being a source of potential energy that could help kick-start new organic processes.
The findings of both of these studies are being used to inform the science mission of NASA’s latest Mars rover, Perseverance, allowing the science team to apply what has been found in Gale Crater to Jezero Crater, to better direct that rover towards places of interest.
“Percy”, to use the nickname for NASA’s latest Mars rover is also being assist in finding places of interest – and the best route to them – by the Ingenuity helicopter. This has now completed its 9th flight , during which it acted directly as an aerial scout for the rover, including the “Raised Ridges”, a feature that suggests it may one once had a water channel beneath it. Ingenuity has also identified a dune field that could result in “Percy” becoming bogged down – as happened with the MER Spirit rover in 2009/10 – ending its mission.
What is particularly fascinating about this work is that the information gathered by Ingenuity can be fed back to Perseverance and used by its auto-drive system to identify local hazards – rocks, etc – the rover can then navigate itself around without having to “‘phone home” for assistance from the Earth-based driving team.
Meanwhile, China’s Zhurong rover is now 2/3rds of the way through its initial 92-day / 90 Sol mission. During that time, the rover has travelled a total of 450 metres, and on July 12th, 2021, it arrived at a special point of study – but one that is neither geological nor meteorological / atmospheric, the rover’s primary science interest.
Instead, the rover had arrived at the impact / landing point for the backshell and parachute that had helped it to reach the ground safely. Following it separation from these during descent, the rover had moved away from it under the power of its lander’s rocket motors ready to make a soft landing. The backshell and parachute continued downward to eventually land some 350 metres from the lander / rover.
Studying both the backshell and parachute helped engineers understand how well both handled the descent through the Martian atmosphere, something that can help inform future missions. At the same time, the rover imaged raised mounds in the region, which could be inverted impact craters or possibly small volcanic domes or other features could be the result of tectonic activity – their nature has yet to be made clear (one of which has been incorrectly labelled as a “outflow delta” in the video below).