Mars has always been the goal of human exploration.
So far, 18 probes have successfully landed on Mars, but whether there is life on Mars is still a question.
High-energy particle impact
For more than a billion years, the soil and rocks of Mars have been bombarded by high-energy particles from cosmic rays. Mostly protons and helium ions, ejected into space by solar flares or exploding stars.
Earth's atmosphere and magnetic field protect us from these particles. But Mars lost its magnetic field about 4.2 billion years ago and much of its atmosphere about 1.5 billion years ago, exposing its surface to cosmic rays.
Since then, solar flares and distant star explosions have been raining high-energy particles across the Earth's surface, potentially erasing chemical evidence of life on Mars in the process.
But all hope of finding life on Mars is not lost, at least for now scientists are looking for places where life has not been wiped out.
Scientists use gamma rays to simulate the collision of high-energy particles in Martian soil. Because gamma radiation has a similar effect to cosmic rays, it is even stronger. They simulated 80 million years of exposure to cosmic rays.
Evidence of life - Amino acids
Martian dirt is mixed with molecules called amino acids. These are the molecules that form proteins, which are the building blocks of most structures in cells. They also produce most of the enzymes that drive the chemical reactions necessary for life.
amino is not unique to life. Ordinary, non-living chemicals can produce hundreds of different chemicals. However, all living things on Earth use only 22 amino acids to build their proteins.
Generally, amino acids produced by living cells tend to be in the L form. The other is type D. Amino acids can come in two different forms; they are chemically the same, but they are mirror images of each other. Chemists call these two forms "left-handed" and "right-handed." The amino acids that make up the proteins of life are basically left-handed, which is the L form, also known as the enantiomer.
Therefore, in theory, the discovery of a group of L-shaped amino acids may be a good sign of life on ancient Mars. Scientists need to understand how long amino acids can survive on Mars and the sampling depth, so that they can predict the abundance of ancient amino acids. Spend.
But cosmic rays break down amino acids faster than scientists realized. In fact, it takes about 20 million years for incoming cosmic rays to destroy the amino acids in the top 10 centimeters of soil and rock, and rover missions as we know them drill into these shallow layers to look for the chemical signatures of life, such as amino acids.
This constant bombardment of charged particles from deep space may have destroyed chemical traces in the top two meters of Martian soil and rock.
We must search for deeper rocks to have a chance of finding chemical evidence of life on Mars.
NASA and my country’s Exploration
NASA’s Perseverance is currently exploring the dry remnants of the river delta. Billions of years ago, the delta was a river that drained water and sediment from the surrounding highlands into Jezero Crater.
If places like this were once teeming with life, those long-extinct creatures might have left behind not only physical fossils but also amino acids and other molecules in sediments and rocks on Mars. By analyzing the chemical composition of ancient riverbed rocks, Scientists hope Perseverance will find chemical evidence.
Not only NASA, but also my country's Mars probe "Zhurong" is also analyzing the chemical composition of Mars. Scientists are conducting analysis. Perhaps in the near future, we will see chemical evidence of life on Mars.
