science

Why some scientists think that life may have started on Mars

Why some scientists think that life may have started on Mars

On February 18th, NASA’s Tenacity spacecraft will parachute through the thin air of Mars, ushering in a new era in exploration of the Red Planet. Landing on Crater LakeLocated north of the Martian equator, it will not be easy. According to NASA, only 40% of the missions sent to Mars are successful. If that happens, persistence could drastically change the way we think about life outside Earth. This is because scientists believe Jezero, a 28-mile-wide crater that used to be a lake, is the ideal place to search for evidence of ancient microbial life on Mars.

Once it lands, Perseverance will collect and store samples of Mars rocks and soil, which will eventually be returned to Earth. This is known as a “sample return mission”, too rare The type of space exploration mission due to its computation. (In fact, there was no mission returning a sample from another planet.) Once the Martian soil returns to Earth within a decade, scientists will begin to study the material to see if there has been ancient life on Mars.

However, some scientists believe that these samples could answer a bigger question: Did life on Earth originate on Mars?

Although the idea that life began on Mars before migrating to Earth seems like a far-fetched hypothesis from science fiction, many famous scientists take this theory very seriously. The general idea of ​​life that begins elsewhere in space before migrating here also has a name: Panspermia. It is the hypothesis that life exists elsewhere in the universe, and is distributed by asteroids and other space debris.

To be clear, the notion that life on Earth originated on Mars is not a dominant theory in the scientific community, but it does seem to be getting attention. Scientists like Gary Rufcon, a professor of genetics at Harvard Medical School, say it sounds “somehow clear”.

The evidence begins with how space debris moved in the young solar system. In fact, we have evidence of rock exchange from Mars to Earth. Mars meteorites are found in Antarctica and around the world – an estimated 159, according to International Meteorite Collector’s Association.

“You could assign it to Mars based on the gaseous inclusions in it, which are a type of equivalent gas that the Viking spacecraft has shown” in the Martian atmosphere, Rovcon said. In other words, the tiny air bubbles in these rocks reveal that they were formed in the air of Mars. “So, there is an exchange between Mars and Earth – often moving from Mars to Earth because it is heading towards a” cliff “, going to Mars” uphill, “from the perspective of gravity.

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But for Ruvkun, whose area of ​​expertise is genomics, it is the timing of cellular life that he believes makes a strong case that life on Earth came from elsewhere – perhaps Mars, or maybe Mars versus another planet.

Rufcon notes that our genomes reveal the history of life, and provide clues to ancestors that preceded us millions or even billions of years. “In our genomes, you can kind of see history, right?” He said. “There is an RNA world that predates the world of DNA and is well supported by all kinds of current biology; therefore, we know the steps evolution took in order to get to where we are now.”

Thanks to advances in genomics, the understanding of LUCA ( The last universal common ancestor) – means the organism from which all life on Earth evolved – progressed significantly. By studying the genetics of all living things on Earth, scientists have a very good understanding of what the unicellular ancestor of every living thing (on Earth) looked like. They also know the timeline: all modern life descended from a single-celled creature that lived about 3.9 billion years ago, that is, only 200 million years after the first appearance of liquid water. In the grand scheme of the universe, this is not long.

And the last universal common ancestor was fairly complex with respect to living things. Rovcon says this leaves two possibilities. “Either evolution to the full modern genome is really easy, or the reason you see it so fast is because we” discovered “life, it didn’t actually start here.” “I like the idea that we just discovered it and that’s why it’s so fast, but I’m strange,” he says.

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If so, Eric Asfog, a professor of planetary science at the University of Arizona, is also an exception. Asfog said that what we know about the oldest rocks on Earth – which have chemical evidence of carbon isotopes, dating back roughly 4 billion years ago – told us that life “began forming on Earth as nearly as soon as it could happen.”

If this is the case, it sets an interesting precedent. “Suppose you expect life to flourish when a planet cools to the point where liquid water can start,” said Asfog. “But once you look at our solar system, which planet is likely to be habitable first?

This is because Mars formed before Earth, Asfog said. Early in Mars’ history when Mars was still cooling, Mars had a “hospitable” environment before Earth.

“If life were to start anywhere, it might start first on Mars,” said Asfog. “We don’t know what the condition is – you know, if it requires something special like The presence of the moon Or some of the factors unique to Earth – but just in terms of where liquid water was first found, it could have been Mars. “

There is an interesting and compelling evidence of how matter traveled between the two neighboring planets. In fact, the further back in time, the more rocks collided between Mars and Earth, Asfugh said. These collision events may be “mammoth Mars massive lumps” launched into space. Such massive asteroids could serve as the habitat of hardy microorganisms.

“When it collides again with a planet, a small fraction of that mountain-sized mass will remain debris on the surface,” he said. “It took a while for the modeling to show that you can survive relatively safely of what we call“ ballistic panspermia ”- firing a bullet at one planet, taking out small pieces, and having them end up on another planet. We think it happens, and the path tends to go from Mars to Earth, more likely than moving from Earth to Mars. “

Asfuj added that surviving in flight, given the vehicle mass of microorganisms, would not be an issue – and neither would be alive on a new, hospitable planet.

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“Any early life form would be resistant to what happens at the tail end of the planet’s formation,” he said. “Any living creature present in the horrific bombardment of collisions should be used, even regardless of that, switching from planet to planet.”

In other words, early microbial life was good in harsh environments and long dormancy periods.

Harvard University professor Avi Loeb told Salon via email that a Martian rock was found on Earth, ALH 84001,Not overheated Along its journey to over 40 degrees Celsius and can endure life. “

All three believe that persistence may be able to add credence to the theory of panspermia.

“If you were to go and search for a remnant of life on Mars, which we hope to do with the Persevering Rover and other Mars adventures, I would be personally surprised if they weren’t tied at the hip to terrestrial life,” said Asfog.

Rufcon said he hopes to be one of the scientists looking for DNA when the Mars sample finally returns.

“Launching something from Mars is very difficult,” he said.

But what does this mean for humans, and our existential understanding of who we are and where we come from?

“In this case, we might all be Martians,” Loeb said. He joked that the self-help book “Men Are From Mars, Women Are From Venus” was probably more right than we know.

Or maybe, as Rufcon believes, we are from a different solar system, and life is scattered throughout the universe.

“To me the idea that everything started on Earth, each solar system has its own small evolution in life taking place, and they’re all independent – it just seems kind of stupid,” Rufcon said. He added, “It is much more explanatory to say, ‘No, it is spreading, it is spreading throughout the universe, and we also discovered it, and it did not start here.’” And at this moment during the pandemic – what a wonderful moment to come up with the idea. Maybe people will eventually believe it. “

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