Curiosity rover finds organic molecules, does that mean there's life?
(Not the main text, this chapter is free for everyone to read.)
According to foreign media reports, NASA held a press conference at 2 pm Eastern Time on June 7 (2 am Beijing time on June 8) 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 it is not enough to prove that life must exist on Mars, these findings are undoubtedly a good thing for future Mars surface and underground exploration missions.
Omen.
Both new discoveries 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 the current course and continue to search for evidence of life." Thomas Zurbu, deputy administrator of the Science Mission Directorate at NASA Headquarters in Washington, said, "I believe that the current and future
Planned projects will make even more amazing discoveries on Mars."
"Curiosity has not yet determined the source of these organic molecules." Jennifer Eigenbrode of NASA's Goddard Space Flight Center, lead author of one of the two papers, pointed out, "Whatever is in the Martian soil
Whether the organic matter is a record of ancient life, food for living things, or has nothing to do with life, it can provide chemical clues related to the Martian environment and evolution process."
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. As far as we know, liquid water is a necessary condition for the existence of life. Curious
Data collected by the probe show that billions of years ago, a lake in Gale Crater once contained all the materials necessary 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 is a very good sign for us. In future missions, we will continue to dig deeper to learn more about the origin of organic molecules on Mars."
"ESA's ExoMars rover will dig deeper, to two meters underground," Eigenbrod explained, "so it is possible to dig out objects that have not been exposed to severe space radiation.
rock."
"It is still possible for the Mars space biological rover to find existing life. But even if it is not found, just analyzing the changes in organic matter from the surface to the depths of the ground is enough to make 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). This fluctuation was detected by Curiosity's Mars Sample Analyzer
” (Sample Analysis at Mars) detected.
This methane may come from the chemical reaction between water and rocks, but scientists have not ruled out the possibility of biological involvement. Previously, scientists have only found methane in the Martian atmosphere in the form of large-scale, irregular plume jets.
This new discovery shows 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 mainly related to biological activities, coming from wetlands, farmland, livestock, etc. It is not yet confirmed whether methane on Mars is related to biological activities.
.But the seasonal fluctuations of methane discovered this time may rule out some geological explanations.
"This is the first time we've seen some sort of repeatability in observations of methane, so it helps us understand it," said Chris Webster of NASA's Jet Propulsion Laboratory, lead author of the second paper.
(Chris Webster) pointed out, "This is all due to the 'longevity' of Curiosity. Without its long-term service, we would not be able to discover this seasonal change pattern."
Methane in the atmosphere of Mars has always been a hot topic in scientific research. Methane cannot remain in the atmosphere for a long time. Since methane is always present in the atmosphere of Mars, it means that there must be a continuous source of methane. Considering the relationship between methane and living things on Earth
To connect, 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. It was found that the methane content in the northern hemisphere was only slightly more than 0.2 parts per billion in winter, but increased in summer.
Rising to 0.6 parts per billion. The research team believes that this methane may be stored in the form of ice
The team is not yet able to confirm the source of methane, but believes it can rule out one explanation - sunlight can break down carbon-containing molecules (organic molecules) in meteorites on the surface of Mars, thereby producing methane. Dr. Webster pointed out that the seasonality of ultraviolet light
The change is not large enough to cause such a change in methane concentration.
This low-angle selfie captures Curiosity drilling into a target rock sample at Mount Sharp in Gale Crater.
To search for organic matter in Martian soil, Curiosity drilled samples of sedimentary rocks (also known as mudstones) from four areas in Gale Crater. These mudstones were formed from sediment that accumulated at the bottom of ancient lakes over billions of years.
The drilled rock samples are analyzed by the Mars Sample Analyzer. The instrument heats the samples in an oven above 500 degrees Celsius, thereby releasing 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 contained sulfur. Eigenbrod said this is related to the addition of sulfur to tires to increase their durability.
The principle of strength is the same, and these fragments are also more stable and durable because of the presence of sulfur.
The results also show that the content of organic carbon is on the order of 10 parts per million, or even more. This is close to the carbon content detected in Martian meteorites, and is about 100 times the amount of organic carbon previously detected on the surface of Mars.
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 types of molecules found in ancient Martian lake sediments and helps explain these molecules.
Why does it survive 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 layers.
"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."
The research was sponsored by the Mars Exploration Mission of the Science Mission Directorate at NASA Headquarters. Goddard Space Flight Center provided the Mars Sample Analyzer. The Jet Propulsion Laboratory built the rover and managed 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? Isn’t 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 it is currently 2018. In just 7 years, there has been no particularly big qualitative change in aerospace engineering. Our science is not what we imagined.
So developed.
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 there is life everywhere in the starry sky... This issue has already been explained in the novel, so I won’t explain it again.