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Mars rover unearths intriguing clues in the hunt for life beyond Earth

Remark

At the bottom of a shallow crater on Mars, the NASA rover Perseverance hit what scientists hope is dirt. Martian rocks excavated by the rover show signs of a watery past and are packed with organic molecules that form the basis for life as we know it.

Scientists on the mission also say the rock samples, which the rover has stored in tubes for a future return to Earth, have the right chemical recipe to preserve evidence of ancient life on Mars, if it ever existed.

The new Perseverance study is described in three comprehensive studies published Wednesday, one in the journal Science and two in the journal Science Advances. The magazine reports are highly technical and devoid of hype – dare to be boring as dirt – but the scientists involved translate them into a more exciting story.

“It’s amazing. We find organics in pretty much every rock,” said Abigail Allwood, a geologist at the NASA Jet Propulsion Laboratory in Pasadena, which pilots the rover and the wider Mars Sample Return mission.

One of the studies concluded that the rocks in the crater experienced three different events where they were exposed to water.

“Critically, the conditions in the rock during each time water migrated through it may have supported small communities of microorganisms,” lead author Michael Tice, a geologist at Texas A&M University, said in an email. In a subsequent interview, he added, “We won’t know until we get the monsters back to Earth.”

On February 18, 2021, NASA successfully landed the Perseverance rover on Mars. Here’s a live video of the landing. (Video: NASA, Photo: NASA/NASA)

Perseverance hit the mark at Jezero crater on February 18, 2021, and has been roaming around it ever since, storing rock samples along the way for later study on Earth. This is an ambitious, multi-stage mission that will require NASA and its partner, the European Space Agency, to send another vehicle to the surface of Mars with the ability to launch samples into orbit. A spacecraft would then bring those samples back to Earth for laboratory testing. The exact timeframe has yet to be determined, but NASA hopes to have the samples on-site by the early 2030s.

This study of Mars is part of the blossoming of astrobiology’s fledgling field, which includes the search for potentially habitable worlds and the first example of extraterrestrial life. Despite the efforts of generations of scientists and despite the claims of UFO aficionados, the discovery of life beyond Earth remains ambitious.

Even finding organics – life-friendly molecules with combinations of carbon, hydrogen and oxygen – is a far cry from discovering life or even proving its presence in the past. Such molecules may be of biological or non-biological origin.

Yet Mars is at the forefront of NASA’s search because it has many beneficial properties. Mars was probably much more like Earth about 3 billion years ago, with warmer and wetter conditions. Life may have existed on Earth and Mars at one time, and it is possible that it originated on Mars and spread to Earth via meteorites. And while its surface is now a barren wasteland, the planet could have liquid water below the surface in significant amounts, and possibly “cryptic” life.

While the Perseverance rover lacks instruments to chemically detect living organisms if they exist today, its instruments allow scientists to study the Martian surface in a level of detail never before possible.

One of the new papers that takes a closer look at the chemistry of Mars has surprised geologists. They had assumed they were going to excavate a pile of sedimentary rock. Instead, the rocks are volcanic.

The Jezero crater was formed at least 3.5 billion years ago during an impact event – a rock that slammed into Mars. The shallow crater clearly had water in it long ago. This could be determined from orbital images of the remains of a delta where a river flowed into the lake. Planetary geologists had assumed that the floor of the crater was covered with sedimentary rock, formed from dirt and debris that slowly accumulated on the lake floor.

If such a sedimentary rock once existed, it is now gone. It may have eroded away, Tice said. The lack of sedimentary rock could mean that the lake didn’t last very long, which would be disappointing to astrobiologists. Life as we know it needs water, and it takes time for more complex life forms to evolve. If it didn’t stick more, life might have struggled to take root.

The volcanic rocks aren’t a disappointment, though, as they hold a ton of information about Mars’ past, including the presence of organic molecules, scientists said. The presence of organic matter on Mars had been confirmed in previous missions, but their precise nature and chemistry cannot be discerned through this kind of long-range study and will require laboratory testing on Earth, said Bethany Ehlmann, a planetary scientist at Caltech and co-author of the paper. two of the new articles.

“Is it just organics that washed into the system — maybe from meteorite material that was just part of the water? That would be the least exciting. Or is it little niches of microbial life living in the cavities of these rocks? That would be the most exciting thing,” Ehlmann said.

She added that the rover is “collecting an amazing array of samples to reveal the environmental history of Mars in all its forms — the volcanic history, the history of water, the relationship of organics to those aquatic environments.”

All this is an attempt to solve the fundamental mystery of Mars: what went wrong? How and when and why did this planet apparently sympathetic to life turn into such a harsh place? The Red Planet may not be a dead planet – the coroner’s report is incomplete – but it certainly looks like it.

Scientists point to something Mars lacks today: a global magnetic field like Earth’s. Such a field protects our atmosphere from the corrosive effects of the solar wind — high-energy particles that stream steadily from the sun and can strip lighter molecules. Mars also lacks plate tectonics, the geological process that on Earth recycles crust and continues to spew water and nutrient-rich lava through active volcanoes.

Somewhere along the way, the magnetic field of Mars died, and then it died became a different kind of planet. It lost almost all of its atmosphere. It became an icy desert world. How quickly this happened is not known, but that could be revealed by the volcanic rocks in the crater.

Magma contains a certain amount of iron, which is sensitive to a planet’s magnetism. As lava cools, it crystallizes into igneous rock, freezing electrons in ferrous minerals into patterns that can reveal the properties of a magnetic field, such as its orientation.

Benjamin Weiss, a planetary scientist at MIT and co-author of two of the papers, said in an email: “All things considered, we’re actually super lucky that there are igneous rocks in the crater and we’re right on it. have landed. , because they are ideal for determining ages and studying the history of the Martian magnetic field.”

Once the mission can return its precious rock collection to Earth, scientists will finally be able to say whether life has ever set foot on Mars — which would raise new questions about whether life, despite the planet’s dramatic transformation, somehow managed to persevere. .

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