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Study for life in the icy crust of the world’s oceans

Study for life in the icy crust of the world's oceans

During 2019 field trials near Greenland’s Summit Station, a high-altitude remote observation station, the WATSON instrument will be pulled through to find signs of life or biosignatures, 110 meters into a borehole. The winch that holds the drill sticks out the top of the drill tent. Credit: NASA / JPL-Caltech

Long before NASA’s Perseverance rover touched the red planet on February 18, one of its highest-level missions was already established: finding evidence of ancient life on the surface of Mars. In fact, the techniques used by one of the scientific instruments on board the rover could have applications on Saturn’s moons Enceladus and Titan as well as Jupiter’s moon Europe.

“Endurance will look for a shopping list of minerals, organic substances and other chemical compounds that can reveal the microbial life that once flourished on Mars,” said Luther Beegle, lead researcher for Mars 2020’s Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals. (SHERLOC) instrument. “But the technology behind SHERLOC, which will look for past life in Mars rocks, is highly adaptable and can also be used to seek out living microbes and the chemical building blocks for life in the deep ice of the moons Saturn and Jupiter.”

Enceladus, Europe and even the obscure moon Titan are believed to hide large oceans of liquid water containing chemical compounds associated with biological processes beneath their thick icy exteriors – very different environments from modern Mars. If microbial life exists in these waters, scientists may also find evidence of it in the ice. But how do you find the proof if it is locked deep inside the ice?

Enter WATSON. Abbreviation for Wireline Analysis Tool for Underground Observation of Northern Ice Sheets, the 3.9-foot-long (1.2-meter-long) long tube-like prototype is under development at NASA’s Jet Propulsion Laboratory in Southern California. It has been linked to Honeybee Robotics’ Planetary Deep Drill, and this combination was successfully tested in extreme cold on Greenland’s ice.

A smaller version of WATSON could one day board a future robotic mission to explore the dwelling potential of one of these enigmatic moons. The instrument scanned into the ice in search of biosignatures – organic molecules created by biological processes. Should it catch sight of anyone, a future version of WATSON with the added ability to collect ice from the borehole wall could then collect samples for further investigation.

Using deep-ultraviolet laser Raman spectroscopy to analyze the materials where they are, rather than immediately retrieving ice samples and then studying them on the moon’s surface, the instrument would provide scientists with additional information about these samples by examining where they are in the connection. of their environment.

Study for life in the icy crust of the world's oceans

WATSON produced this fluorescence map over a borehole at a depth of 307.7 feet (93.8 meters) in Greenland’s ice. The left panel shows nebulous blobs of biosignatures, and the right panel shows a colored version that groups similar organic chemicals. Credit: NASA / JPL-Caltech

“It would be great if we first looked at what these samples actually looked like in their natural environment before scooping and mixing them up in a slurry for testing,” said Mike Malaska, an astrobiologist at JPL and lead researcher for WATSON . “Therefore, we are developing this non-invasive instrument for use in icy environments: to take a deep look into the ice and identify clusters of organic compounds – perhaps even microbes – so that they can be examined before we further analyze them and lose their original context or change their structure. “

Although WATSON uses the same technique as Perseverance’s SHERLOC, there are differences. First, SHERLOC will analyze marsh rocks and sediment to hunt for evidence of past microbial life that can be collected and returned to Earth by future missions for deeper investigation. And SHERLOC does not drill holes. A separate tool does that.

But both rely on a deep ultraviolet laser and a spectrometer, and where the WATSON ice instrument has an image processing to observe texture and particles in the ice wall, Perseverance’s SHERLOC is paired with a high-resolution camera to take close-ups of stone textures in support of its observations. This camera happens to share the same name as the ice research prototype: WATSON. In this case, however, the acronym stands for Wide Angle Topographic Sensor for Operations and eNgineering. (After all, any instrument with a name inspired by the famous fictional detective Sherlock Holmes is bound to inspire references to his partner.)

Enceladus on earth

Just as SHERLOC underwent extensive testing on Earth before going to Mars, so must WATSON do so before being sent to the outer solar system. To see how the instrument can work in the icy crust of Enceladus and the moon’s extremely low temperatures, the WATSON team chose Greenland as a “Jordan analogue” for field tests of the prototype during a 2019 campaign.

Jordan analogues share similar properties with other locations in our solar system. For Greenland, the environment is near the middle of the island’s inland ice and away from the coast, approximately the surface of Enceladus, where sea materials erupt from the small moon’s lush vents and rain. The lack of ice on the outskirts of Greenland’s glaciers near the coast can meanwhile serve as an analogue to Europe’s bulging deep, icy crust.

Study for life in the icy crust of the world's oceans

During the field test, WATSON and its attached drill were lowered into the borehole to a depth of up to 110 meters deep. In this image, WATSON’s optical window allows the instrument to “see” the sides of the borehole. Credit: NASA / JPL-Caltech

During the campaign to explore an existing borehole near Summit Station, a high-altitude remote observation station in Greenland, the instrument was put through. As it fell more than 100 meters down, WATSON used its UV laser to illuminate the ice walls and made some molecules glow. The spectrometer then measured their faint glow to give the team insight into their structure and composition.

While finding biosignatures in Greenland’s ice pack did not come as a surprise – the tests were after all on Earth – mapping their distribution along the walls in the deep borehole raised new questions about how these features got where they are. The team discovered that microbes deep inside the ice tend to clump together in blobs, not in layers, as they originally expected.

“We created maps when WATSON scanned the sides of the borehole and the cluster points for blue greens and reds – all representing different kinds of organic material,” Malaska said. “And what was interesting to me was that the distribution of these hotspots was pretty much the same everywhere we looked: whether the map was created at 10 or 100 meters [33 or 330 feet] deep down, these compact little blobs were there. “

By measuring the spectral signatures of these hotspots, the team identified colors that were consistent with aromatic hydrocarbons (some that may originate from air pollution), lignins (compounds that help build cell walls in plants), and other biologically produced materials (such as complex organic acids). also found in soil). In addition, the instrument registered signatures corresponding to the glow produced by microbus clusters.

There are more tests to be performed – ideally in other Earth analogues approaching the conditions of other icy moons – but the team was encouraged by how sensitive WATSON was to so many different biosignatures. This high sensitivity would be useful on missions to marine worlds where the distribution and density of any biosignatures are unknown, said Rohit Bhartia, lead researcher for WATSON and deputy lead researcher for SHERLOC from Photon Systems in Covina, California. “If we were to collect a random sample, we would probably miss something very interesting, but through our first field trials we are able to better understand the distribution of organic matter and microbes in soil ice that can help us when we drills into the crust of Enceladus. “

The results of the field test were published in the journal Astrobiology in the fall of 2020 and presented at the American Geophysical Union Fall Meeting 2020 on December 11th.

The detective aboard NASA’s Perseverance Rover

More information:
Michael J. Malaska et al. Underground detection of microbes and various organic matter hotspots in the Greenland ice sheet, Astrobiology (2020). DOI: 10.1089 / ast.2020.2241

Citation: Probing for life in the iskyust of ocean worlds (2021, April 7) retrieved April 8, 2021 from https://phys.org/news/2021-04-probing-life-icy-crusts-ocean.html

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