Beneath Deep Space

(Not the main text, this chapter is free for everyone to read.)

According to foreign media reports, NASA held a press conference at 2 p.m. Eastern Time on June 7 (2 a.m. on June 8, BJ time) and announced two important discoveries about Mars: 1. The Curiosity Mars Rover Organic molecules were found in a 3 billion-year-old sedimentary rock near the surface of Mars, indicating that ancient life may have existed on Mars;

2. It was discovered that the methane content in the Martian atmosphere has seasonal fluctuations, which may be related to modern Martian life. Although not enough to prove that life exists on Mars, these findings are undoubtedly a good sign for future exploration missions on the surface and underground of Mars.

The two new findings were published in the June 8 issue of Science.

Organic molecules are made of carbon and hydrogen, and may also include oxygen, nitrogen, and other elements. Although usually associated with life, organic molecules can also be produced through non-biological processes and are not necessarily evidence of life.

"Mars is telling us with these new discoveries: stay on course and continue to search for evidence of life." Thomas Zurbuchen, deputy administrator of the Science Mission Directorate at NASA Headquarters in Washington, said, "I believe in the current and future plans The projects being carried out will make more amazing discoveries on Mars.”

"Curiosity has not determined the source of these organic molecules." Jennifer Eigenbrode, lead author of one of the two papers and NASA's Goddard Space Flight Center, pointed out, "Whatever organic matter in the Martian soil Whether it is a record of ancient life, food for living things, or not related to life, it can provide chemical clues related to the Martian environment and evolution. "

Although the surface of Mars is not suitable for life today, there is clear evidence that the Martian climate in ancient times once allowed liquid water to accumulate on the surface and form lakes. And as far as we know, liquid water is a must for life. Data collected by Curiosity shows that billions of years ago, a lake in Gale Crater contained all the necessary materials for life, including chemical building blocks and energy sources.

"The surface of Mars is exposed to cosmic radiation. Both radiation and irritating chemicals can decompose organic matter." Eigenbrod pointed out, "This time, ancient organic molecules were found in the top 5 centimeters of sedimentary rocks formed during the habitable period of Mars. , which bodes well for us as we continue to dig deeper in future missions to learn more about the origins of organic molecules on Mars.”

"ESA's ExoMars rover will dig deeper, to two meters underground," Eigenbrod explained, "so it will be possible to dig out objects that have not been exposed to severe space radiation. rock."

"It's possible that the Mars Space Biological Rover will find existing life. But even if it doesn't, just analyzing the changes in organic matter from the surface to deep underground will be enough to yield surprising discoveries."

Methane on Earth can exist in the form of "combustible ice." What about Mars?

In the second paper, scientists describe seasonal fluctuations in methane levels observed in the Martian atmosphere over the past three Martian years (about six Earth years). The fluctuation was detected by Curiosity's Sample Analysis at Mars.

The methane may come from chemical reactions between water and rock, but scientists have not yet ruled out a biological connection. Previously, scientists had only discovered methane in the Martian atmosphere in the form of large, irregular plumes. The new findings show that the small amount of methane contained in Gale Crater increases during warm summers, reaches a peak, and then decreases again in winter, every year.

This discovery is important because it will help narrow down the possible sources of methane. Methane on Earth is primarily related to biological activity, coming from wetlands, farmland, livestock, and more. It is not yet confirmed whether methane on Mars is related to living things. But the seasonal fluctuations in methane discovered this time may rule out some geological explanations.

"This is the first time we've seen some kind of repeatability in observations of methane, so it helps us understand it." Chris Webster of NASA's Jet Propulsion Laboratory, lead author of the second paper Chris Webster pointed out, "This is all due to Curiosity's 'longevity'. Without its long-term service, we would not be able to discover this seasonal change pattern."

Methane in the Martian atmosphere has been a hot topic of scientific research. Methane cannot remain in the atmosphere for long. Since methane is always present in the Martian atmosphere, it means there must be a continuous source of methane. Given the connection between methane and life on Earth, scientists must solve this Martian mystery.

Curiosity has been searching for traces of methane in the Martian atmosphere since it landed in Gale Crater at the equator of Mars in 2012. The results found that methane levels in the northern hemisphere are just above 0.2 parts per billion in winter, but rise to 0.6 parts per billion in summer. The research team believes that this methane may be stored in the form of ice

The team has not been able to confirm the source of the methane, but believes it can rule out one explanation - that sunlight can break down carbon-containing molecules (organic molecules) in meteorites on the Martian surface, thereby producing methane. Dr. Webster noted that seasonal changes in ultraviolet light are not large enough to cause changes in methane concentrations of this magnitude.

This low-angle selfie captures Curiosity as it drills for a target rock sample in Gale Crater's Mount Sharp.

To search for organic matter in Martian soil, Curiosity drilled samples of sedimentary rocks, also known as mudstone, from four areas in Gale Crater. These mudstones formed over billions of years from sediment that accumulated at the bottom of ancient lakes. The drilled rock samples are analyzed by the Mars Sample Analyzer. The instrument heats the sample in an oven to temperatures above 500 degrees Celsius, which releases organic matter from the powdered rock.

The Mars Sample Analyzer detected small organic molecules - fragments of larger organic molecules that cannot easily evaporate - in material released from the mudstone samples. Some of the fragments contain sulfur. Eigenbrod said that in the same way that sulfur is added to tires to increase their durability, these fragments are also more stable and durable because of the presence of sulfur.

The results also show that the amount of organic carbon is on the order of 10 parts per million, and possibly more. This is close to the amount of carbon detected in Martian meteorites and about 100 times the amount of organic carbon previously detected on the Martian surface. The molecules identified this time include thiophene, benzene, toluene, etc., as well as short carbon chains such as propane and butene.

In 2013, the Mars Sample Analyzer discovered some chlorine-containing organic molecules in rocks in the deepest part of Gale Crater. This new discovery further enriches the variety of molecules found in ancient Martian lake sediments and helps explain why these molecules have survived to this day.

After the discovery of methane in the Martian atmosphere and the discovery of organic molecules preserved from ancient times near the surface, scientists have greatly strengthened their confidence that NASA's 2020 Mars Rover and ESA's ExoMars ) The rover will also discover more organic matter on the Martian surface and in shallow subsurface.

"Do these findings indicate the existence of life on Mars?" asked Michael Meyer, chief scientist of NASA's Mars Exploration Project. "We don't know yet. But these results show that we are on the right track."

This research work was sponsored by the Mars Exploration Mission of NASA Headquarters' Science Mission Directorate. Goddard Space Flight Center provides the Mars Sample Analyzer. The Jet Propulsion Laboratory is responsible for building the rover and managing the project for the Science Mission Directorate.

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A few comments from the author:

The organic matter analysis instrument of "Curiosity" is actually a relatively simple instrument. It uses heating to decompose large molecular organic matter and release them, and then simple organic molecules can be analyzed.

For example, what we got this time: thiophene, benzene, toluene, etc.

The actual organic matter contained in the soil is likely to be more complex than these due to heating.

Whether it is life or not is unclear.

Some people will definitely say: Why not launch a more powerful detection instrument? Is this organic matter analysis instrument too simple?

Because Curiosity is already at the limit of current technology, or close to the limit. It was launched in 2011 and is currently in 2018. In just 7 years, the aerospace engineering has not undergone any major qualitative changes. Our science is not as developed as imagined.

It may take decades to truly confirm whether there is life.

I hope our country can also contribute to this project.

Also, if life on Mars is really discovered, or life once existed, it will not necessarily be a good thing for us (human beings).

The more complex life is discovered, the more bad news it is...

Because that means that there is life everywhere in the starry sky... This issue has already been explained in the novel, so I won't explain it again.