Space Sunday: life, planet, moons and robots

Scientists using data from NASA’s Curiosity rover measured the total organic carbon – a key component in the molecules of life – in Martian rocks for the first time, and have discovered that there is potentially more to be found on Mars than in the driest environments to be found here on Earth.

Organic carbon is carbon bound to a hydrogen atom and is the basis for organic molecules; they are created and used by all known forms of life, and it has been previously detected within Martian rock samples studied by the rover. However, the key difference between those results and those published within this study is that other attempts to examine rock samples for the presence of carbon have only looked for specific compounds that contribute to organic carbon or only represented measurements capturing just a portion of the carbon in the rocks; this study presents the total amount of organic carbon detected in samples gather by the rover during an intensive examination of exposed rock made in 2014.

Total organic carbon is one of several measurements [or indices] that help us understand how much material is available as feedstock for prebiotic chemistry and potentially biology. We found at least 200 to 273 parts per million of organic carbon. This is comparable to or even more than the amount found in rocks in very low-life places on Earth, such as parts of the Atacama Desert in South America, and more than has been detected in Mars meteorites.

– Jennifer Stern, NASA Goddard Space Flight Centre, Maryland

To make the measurement, Curiosity delivered the sample to its Sample Analysis at Mars (SAM) instrument, where an oven heated the powdered rock to progressively higher temperatures. This experiment used oxygen and heat to convert the organic carbon to carbon dioxide (CO2), the amount of which is measured to get the amount of organic carbon in the rocks. Adding oxygen and heat allows the carbon molecules to break apart and react carbon with oxygen to make CO2. Some carbon is locked up in minerals, so the oven heats the sample to very high temperatures to decompose those minerals and release the carbon to convert it to CO2. While the samples were gathered and analysed in 2014, it has taken years of ground-based analysis to fully understand the data and to put the results in context of the mission’s other discoveries at Gale Crater to reach a point of being ready for publication.

A mosaic of images captured by the Curiosity rover of the “Yellowknife Bay” rock formation, the location where the rover carried out its extensive search for carbon isotopes. The sedimentary rocks within the formation were laid down by an ancient stream and a lake that might have also contained the ingredients for life. “Yellowknife” was exposed about 70 million years ago by the removal of overlying layers due to erosion by the wind. Courtesy NASA/JPL / MSSS

A specific interest of the study was to identify the carbon isotope ratios. Isotopes are versions of an element with slightly different masses due to the presence of one or more extra neutrons in the nucleus of their atoms. In particular, two of the most common carbon isotopes are Carno-13, with seven neutrons tends to be of largely inorganic origin, while Carbon-12, with six neutrons, tends to be more associated with organic processes – and the study found this to be more abundant than had been anticipated.

But this doesn’t mean that it is absolute evidence that life may have formed on Mars. While the planet was once much warmer and wetter, with a dense atmosphere and free-flowing water on the surface that may have given rise to life, it’s important yo note the “more” used above for Carbon-12 -it can also be the result of non-organic processes such as vulcanism; and Mars was once extremely volcanically active.

Nevertheless, the confirmation that rock samples studied by Curiosity are richer than expected in Carbon-12, coupled with the general environment know to have once existed in Gale Crater – a place that once have an abundance of water and energy sources – further points to the crater being very conducive to life perhaps having gained a toehold there.

Exomoons as the Abode of Life?

We’re all familiar with the Star Wars franchise of films and TV series. In 1977, the original film in the series depicted a rebel base on the fourth moon of the fictional gas giant Yavin.

Many probably didn’t pay much attention to this at the time – beyond noting how the planet played a crucial role in keeping the base shielded from the Death Star, and its cool appearance in Yavin 4’s sky; however, the film was, in many respects well ahead of its time in its depiction of a  habitable Moon. In 1977, the exact nature of moons like Jupiter’s Europa and Saturn’s Enceladus as places of ice and, possibly, water, was suspected rather than known, whilst guesses were also being made about what might lie under the atmosphere of Titan. It would be a couple of decades before we really started to understand the potential for some of the Moons of our outer solar system to have the conditions in which basic life might gain a hold.

The idea of a moon of a planet being habitable was an idea ahead of its time when visualised in the original Star Wars film, but given what we’ve come to understand about the moons in our own solar system, such potentially life-hosting places may exist elsewhere in our galaxy. Credit: 20th Century Fox / LucasFilm / Disney

While our own solar system moons like Europa are cold place and any life than may form within them sitting within an evolutionary cul-de-sac, the mechanics that make them potentially life-bearing is now being looked at as having the potential to make exomoons like Yavin 4 possible elsewhere in the galaxy.

The major factor in the life-bearing potential of places like Europa and Enceladus is that of tidal forces. In short, as these moons orbit their parents, they are subject to the gravity of the planet exerting a pull on them at the same time as the other moons orbiting the planet also exerting forces on them, all of which causes the moon to “flex”, heating its interior. With Europa and Enceladus, this heating may have resulted un liquid water oceans being possible under their icy surfaces.

Of course, such is the distance between the Sun and these Moons of Jupiter and Saturn than the moons don’t get enough solar heating to remain warm. However, a lot of exoplanets orbit their parent stars a lot closer than our gas giants do to the Sun. While some are clearly too close to their parent, forming what are called “hot Jupiters”, others are at a distance such that any Moons orbiting them could be subject to both tidal action and receive enough solar heating to maintain a potentially temperate atmosphere.

There are question marks around the theory – would such moons be tidally locked with their parent planet, such that the same side of the moon always faces the planet and the same face facing the local star? Would the planet itself be tidally locked to its parent star? How would the atmosphere of a moon fare caught between the outflow of radiation from both star and planet? However, it also promises a new avenue of research for exoplanets and exomoons and the search for signs of life elsewhere in the galaxy, as has been proposed in a paper published in the Astronomical Journal.

What is particularly interesting about the paper is that while the team behind it initially focused on gas giants and their possible moons, their computer modelling suggests that solid rocky planets of the size of Earth or a little bigger / heavier that have Moons could actually become far more habitable themselves.

Could moons orbiting the planets in the “goldilocks zone” of TRAPPIST-1 help those planets avoid becoming tidally locked with their parent, and thus be more naturally temperate and amenable to life than might otherwise be the case. Credit: NASA

This is because the majority of Earth-sized worlds, such as those of the TRAPPIST-1 seven-planet system are so close to their parent star so as to be tidally locked, so with one side in perpetual heat and the other in perpetual cold (and darkness), it would be hard for them to offer a foothold for life. However, should such worlds have a reasonably-sized moon orbiting them in a 2:1 resonance, the team’s results showed the planet would itself be far more likely to maintain its own axial spin, thus helping to even-out temperatures across its surface and possibly help maintain an atmosphere.

Thus the importance of exomoons as aiding life, either by supporting it directly or by helping their parent planet remain habitable, has gained further significance, as has the detection of such moons by direct infra-red and spectrographic analysis of their parent worlds by the likes of James Webb Space Telescope and the Extremely Large Telescope.

Walking on the Moon

With humans on the cusp of a return to the Moon, notably via the US / International Artemis programme, a lot of research is going into support systems crews on the Moon will require , such as surface rover vehicles and robot assistants capable of going where astronauts might encounter issues – such as climbing down the steep walls of craters while an astronaut might easily fall.

These robot assistants are being developed by a range of companies and agencies around the world, and one of those with considerable experience in the field is the German Space Agency (DLR). They have come up with a range of small rovers that can operate autonomously or via tele-operation be crews within pressurised environments such as a rover or a base station – or even from orbit.

For the last couple of months, DLR have been testing some of their designs on the upper slopes of Mount Etna, Italy, where the volcanic ash and loose lava is of a similar consistency to lunar regolith. One of the most intriguing of these robots is called Scout, a squat vehicle with a segmented body and which travels not on wheels or tracks, but on rotating “legs” that allow it to “run” over loose ground with relative ease.

The DLR Lunar Scout walking on the slopes of Mount Etna. Credit: DLR

Fitted with camera systems and capable of carrying science instruments within its segments, Scout could be used to both  scout for safe routes through difficult terrain than astronauts might then use, and to carry out science functions of its own.

NASA Uses Cygnus to Boost the ISS Orbit

Not long after Russia invaded Ukraine, the head of Roscosmos, Dmitry Rogozin went on a bit of a Twitter / television bender, making a series of aggressive statements regarding Russian co-operation with the United States and the West in the matter of space activates and the International Space Station.

With regards to the latter, one of Rogozin’s claims was that Roscosmos could refuse to use their Progress resupply vehicles to carry out periodic “boosts” to the station’s orbit – required because, even at 450 km altitude, there is still sufficient drag exerted by the very tenuous atmosphere to cause the station to very slowly spiral back towards Earth. Since the US retired the space shuttle, Russia has carried out these boosts using their Progress vehicles. While Roscosmos pushed back against Rogozin’s rants, emphasising continued cooperation with the west with regards to the ISS.

Cygnus NG-17 docked with the ISS. Credit: NASA

After Rogozin’s threat concerning the required boosts, the US said little, other than noting Progress was not the only option for raising the station’s orbit. In particular, there are two other vehicles with the propulsive capabilities able to perform the task: the Japanese Kounotori HII Transfer vehicle and the American Cygnus craft.

The latter of these performed a proof-of-concept attempt, raising the station’s orbit by 90 metres, but given the use of Progress, nothing further was tried. So, in the light of Rogozin’s comments, and with Cygnus NG-17 docked with the ISS (it had arrived in February 2022), NASA decided to use the vehicle to carry out a required ISS orbital boost.

The first attempt to do so was made on June 20th, but a data hiccup caused the Cygnus vehicle’s motor to cut after just 5 seconds. A further attempt was made on June 25th, with a 301-second engine burn raised the station’s perigee by 0.8 km and apogee by 0.2 km. With the move a success, NG-17 – called Piers Sellers in memory of the Anglo-American astronaut who passed away in 2016 – departed the station on June 28th, loaded with trash and waste from the ISS and performed a controlled re-entry into the denser atmosphere to burn up.