The identical know-how might search for microbes in Martian rocks or below the ice on Europe

By On Apr 13, 2021

Since landing in Jezero Crater on February 18, 2021, the Perseverance rover has been preparing its scientific instruments to search for signs of past life on the Red Planet. These include spectrometers that scan Martian rocks for organic matter and minerals that form in the presence of water, and a caching system that stores samples of Martian soil and rocks so that they can be retrieved for a future mission.

These tell-tale indicators could be past life signs that would most likely appear in the form of fossilized microbes. In the near future, a similar tool could be used to search for extraterrestrial life today. It is known as a wired analysis tool for underground ice sheet observation in the north (WATSON) and could be used to find evidence of life in “ocean worlds” such as Europe, Enceladus and Titan.

Beyond Earth, Mars is the most habitable body in the solar system – at least when it comes to life as we know it. While the Martian environment is pretty harsh today, multiple pieces of evidence have confirmed that it was once a warmer, wetter place. In addition to a denser atmosphere, Mars also had abundant water on its surface in the form of rivers, lakes, and an ocean that covered much of the northern hemisphere.

The tether (which contains the power cord and data feed) attaches to the top of the WATSON and the drill. Photo credit: NASA / JPL-Caltech

This, of course, has raised questions about whether Mard could have supported life in the past. To investigate this, Perseverance has an instrument called Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC). Using cameras, spectrometers and a UV laser, SHERLOC searches for minerals and organic molecules associated with biological processes (also known as “biosignatures”).

Luther Beegle, the lead researcher for the Mars 2020 SHERLOC instrument, recently stated in a NASA press release:

“Perseverance will look for a shopping list of minerals, organics, and other chemical compounds that may reveal microbial life on Mars. However, the technology behind SHERLOC, which searches for past life in Martian rocks, is extremely adaptable and can also be used to find living microbes and the chemical building blocks for life in the deep ice of the moons of Saturn and Jupiter. “

Beyond Mars, many scientists believe that moons like Europa, Enceladus, and Titan are the most likely places to find evidence of extraterrestrial life. It is believed that beneath their icy exterior, these moons have huge oceans of liquid water that contain the chemical compounds associated with biological processes. Combined with hydrothermal activity at the core-mantle boundary, it is possible that these moons also contain life.

The WATSON instrument after being removed from the drill at Summit Station for inspection. Photo credit: NASA / JPL-Caltech

Unfortunately, it is a great challenge to find evidence of this life. Unlike Mars, scientists may not be able to find evidence that it is trapped in the surface ice. In order to penetrate deeper into the watery environments hidden below, instruments of a different type are required. This is where the WATSON instrument developed by NASA’s Jet Propulsion Laboratory (JPL) comes into play.

This prototype is essentially a 1.2 meter tube that can be used to take samples from the depths of an ice sheet. WATSON was recently coupled with Honeybee Robotics’ Planetary Deep Drill (PDD), which can also be used to take drill samples for geological (and astrobiological analysis). The combination was successfully tested in the extreme cold of the Greenland ice sheet.

This environment was chosen for a campaign in 2019 as it approaches the conditions on the surface of icy moons. Saturn’s moon Enceladus, for example, is known to experience periodic eruptions in its southern polar region, where hydrothermal vents deep beneath the ice cause water and organic molecules to spray through cracks in the surface.

In Greenland, the icy sheet in the middle of the landmass and off the coast is a suitable “earth analogy” for Enceladus, while the mangled ice on the edge of the glaciers near the coast can serve as an analogue for the rough and deep sections of Europe’s icy crust. For the 2019 campaign, WATSON was used in an existing borehole near Summit Station, a high-altitude remote observation station in Greenland.

WATSON fluorescence map showing nebulous blobs of biosignatures (left) and the grouping of similar organic chemicals (right). Photo credit: NASA / JPL-Caltech

After being integrated into the PDD, WATSON was lowered more than 100 meters below the surface. There it illuminated the walls of the ice with its UV laser, causing some of the molecules to glow. The weak light generated was measured with a spectrometer to give the research team an insight into the structure and composition of these molecules (as well as their distribution).

The results were then converted into a map (shown above) to show the grouping of molecules based on similar chemical compositions consistent with both natural and man-made compounds. These included aromatic hydrocarbons (which come from air pollution and / or rotting plant material), organic polymers in the supporting tissue of plants (lignins), complex acids in the soil, and other organic molecules.

In addition, the instrument recorded spectral signatures similar to those produced by clusters of microbes. From this, the team found that deep in the ice, microbes are not distributed in layers (as previously expected), but tend to clump together in blobs. As Malaska described it:

“We created maps when WATSON was scanning the sides of the borehole and cluster hotspots of blues, greens, and reds – all different types of organic material. And what interested me was that the distribution of these hotspots was pretty much the same everywhere we looked: regardless of whether the map was drawn at 10 or 100 meters [33 or 330 feet] In the depths there were those compact little blobs. “

Artist’s impression of the Honeybee Robotic PDD used on the surface of Europe. Photo credit: Honeybee Robotics

Although there is still a lot of testing to be done before the technology can be used in an alien environment, the team was very encouraged by how sensitive WATSON was to a wide variety of biosignatures. This is very useful when it comes to performing missions in ocean worlds where the distribution and density of potential biosignatures is currently unknown.

Rohit Bhartia, principal investigator for WATSON and assistant principal investigator for SHERLOC (at Photon Systems) said:

“If we collect a random sample, we are likely to be missing out on something very interesting, but our initial field tests will allow us to better understand the distribution of organics and microbes in terrestrial ice that could help us drill into the Enceladus crust. “

In the near future, a smaller version of WATSON could be included on board a future robotic mission to one of these moons – such as the proposed Europa Lander concept. The instrument could scan into the surface ice of these bodies to look for signs of organic molecules associated with biological processes.

These could be returned to Earth as part of a sample return mission or analyzed on site using a Raman spectroscopic instrument with a deep ultraviolet laser. This latter method would be preferable in some ways as it would allow astronomers to study potential biosignatures in the context of their environment.

Artist’s impression of a possible Europa Lander mission that would explore the surface of the icy moon in the coming decades. Photo credit :: NASA / JPL-Caltech

Mike Malaska, JPL astrobiologist and senior scientist at WATSON, said:

“It would be great if we could first examine what these samples actually look like in their natural environment before scooping them up for testing and mixing them into a slurry. For this reason we are developing this non-invasive tool for use in icy environments: to get a deep insight into the ice and to identify clusters of organic compounds – possibly even microbes – so that they can be examined before we analyze them further and their native lose context or change their structure. “

As the name suggests, there is a certain relationship between the SHERLOC and WATSON instruments. While they may differ in details, they are ultimately very similar in terms of purpose. Both rely on a deep ultraviolet laser and spectrometer to identify biosignatures, and both rely on high-resolution cameras to get close-ups of what they find.

And with luck, both will contribute to some of the greatest scientific breakthroughs ever made. In short, they could help us finally answer the question, “Is there life beyond earth?”

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