How did life arise? Nowadays, there are various opinions on where life came from. Joseph Cashbink, a professor at the California Institute of Technology in the United States, believes: "The ancient life was not born on the earth, but came from Mars." 4 billion years ago Joseph Ca

How did life come about? Nowadays, there are various opinions on where life came from. Professor Joseph Cashbink of California Institute of Technology in the United States believes: "The ancient life was not born on the earth, but came from Mars."

4 billion years The Earth Before

Joseph Cashbink of the California Institute of Technology discovered a 3.8 billion-year-old rock in Greenland called "black shale."

Kashbink said: "When you look at black shale, you see a beautiful thin layer. These rocks are sheltered from the rough waves of the water, which means they are deeper in the ocean. Formed. In fact, almost all the rocks we see from 4 billion years ago indicate that the Earth was a world with only oceans. "

billion years ago, the Earth was a far cry from what it is today, with almost no land. A planet with only oceans. Many scientists believe that Earth's giant "continents" formed about 2.7 billion years ago, or later, thanks to increased volcanic activity at that time.

Kashbink continued: "In order to form life, you need to make large molecules from organic matter, and it is not easy to do this because 4 billion years ago, there was no land on the earth and it was all covered by oceans. If there were Too much water and the reaction won't work. Mars, on the other hand, has land and oceans, so if you compare the two planets 4 billion years ago, Mars would be more suitable for life."

Death Valley The birth process of life

Cashbink believes that the best place to understand the environment of Mars 4 billion years ago is in Death Valley, California .

With only 50 millimeters of precipitation per year, Death Valley is a stretch of dry land. Kashbink came to Badwater, the heart of the region.

In Badwater, the center of the Death Valley region, the area here is surrounded by white crystals, and a strange sight spreads. Cashbink picked up a handful of some kind of crystal about 2 centimeters thick, licked it, and then said: "Salty." This is natural salt.

"These are the salt stains left behind by the evaporation of large lakes that once existed. Death Valley is the lowest place on the North American continent, and a large amount of water flows into it. Over time, the water here evaporates and the elements in it become concentrated , they became these crystals . Here you can see traces of the former lake.”

Kashbink then pointed to a cliff a few hundred meters away, with a faint black line on it. That's where the water used to be. The waves came in and chipped away at the rocks.

This used to be a lake. But as it dries, the components in the water become concentrated. Cashbink believes that it is this kind of dry land that is ideal for the birth of life. The formation of Death Valley is the process of the birth of life.

Why is water necessary for organic life?

All life has "DNA" (DNA) consisting of two strands. DNA was originally thought to be produced from a strand of "RNA" (ribonucleic acid).

RNA is a long chain of organic material called " nucleotide ". Nucleotides are also made up of linked parts called " base ", " deoxyribose " and " phosphate ".

The process from bases, deoxyribose and phosphate to DNA involves several gates.

The first hurdle is the synthesis of nucleotides. In order to join these parts, water molecules need to be removed. If there is too much water, it will be difficult to react.

The environment to solve this problem is in Death Valley.

Kashbink said this was indicated by the small rocks rolling around. At first glance, the rock looks unchanged, but if you look closely, you can see that it is formed by a crack in a large rock.

"When it rains, the salt will melt into water and then enter the cracks of the rock. Soon after it dries and the water evaporates, the salt will form crystals in the rock. When this crystal forms, the rock will crack due to the force of expansion. "

The presence of cracked rocks indicates that the inflow and drying out of water occurred repeatedly in Death Valley.

"To produce life, complex DNA must be formed from simple organic matter. One of the most suitable environments for this is a dry place. Because life is produced by removing water molecules to connect organic matter, a dry environment is required."

in When synthesizing nucleotides, an environment on land with repeated inflows of water and a dry environment is ideal. And from the latest detection, we know that the same environment existed on ancient Mars.

The rock used as evidence was found on Meridiani Planitia where the Mars rover Opportunity landed. On that rock, there are several long and thin cracks, which are thought to be caused by the same structure as the broken rocks seen in Death Valley.

In addition, the rover also discovered a mineral called Jarosite. On Earth, this is a mineral found where water dries up. Based on this evidence, Kashbink believes that on ancient Mars, as in Death Valley, water flowed in and dried out repeatedly.

Four billion years ago, Mars had an environment that was completely watery and that was not found on Earth. In this environment, the conditions for life can be born.

Mastering the key substances for the birth of life

Mars, with its oceans and land, can be said to have provided an ideal environment for the synthesis of nucleotides, the first step in the creation of DNA for life. So in the next step, how to achieve RNA synthesis?

When nucleotides are present in water, they do not bind as they do. This is because they break down over time. For 30 years, James Ferris (who passed away in 2016), a professor at Rensselaer Polytechnic Institute in the United States, who has continuously explored the birth process of life through experiments, found the key to solving this problem.

Feliz said in an interview before his death: "We were studying the clay mineral and found a clay called montmorillonite . This is important because it has the power to promote chemical reactions in RNA. When montmorillonite is used in the synthesis, the reaction will be completed in one go. "

In fact, Feliz and others conducted related experiments using montmorillonite. Add a small amount of montmorillonite and activated nucleotide solution to the test tube and stir. After 3 days, it was measured with a measuring device that the longest number of nucleotides was connected to 15. In just 3 days, 15 nucleotide ligations were produced.

In fact, montmorillonite is a charged layer from a microscopic perspective. Through the force of electricity, the nucleotides are attracted between the layers. Each molecule is neatly aligned on the clay in a specific direction. As a result, the binding efficiency is very high.

Felice said excitedly: "This discovery is very important. With montmorillonite, you can line up a long list of molecules. We have connected 50 in the past. In other words, as long as there is montmorillonite, life will be born." The possibility is very high. "

may hold the key to the birth of life. This amazing clay is also found on Mars. In 2009, the MRO probe discovered clay thought to be montmorillonite in part of the Meridiani Plain.

In other words, there are two conditions necessary for the production of DNA and RNA for life on Mars, namely repeated inflow of water and a dry environment, as well as montmorillonite.

"Our mother star is Mars!"

Kashbink pointed out that Mars 4 billion years ago was more favorable for the birth of life than the earth with only seas.

"Where was life born? I don't think it was the earth full of water 4 billion years ago. At that time, there were seas and dry land on Mars.The crater's depressions turned into lakes, where water flowed in and evaporated repeatedly. The environment of ancient Mars may be connected with the birth of life. Our mother planet is Mars and I think we are Martians . "

If life was born on Mars, how did it come to the earth?

In response to this doubt, Kashbink said that there is a very suitable "spaceship" to move from Mars to the earth. That is Meteorites .

According to Kashbink’s conception, the ancestors of life were born on Mars 4 billion years ago, and then came to the earth in a small spacecraft called a meteorite.

Then, meteorites are again. How did it fly from Mars to Earth?

The scenario that Cashbink thought about is this. 4 billion years ago, microorganisms produced on Mars also lived in rocks. One day, countless asteroids crashed on Mars. The debris flew out of space, and after a long journey into space, some of the microorganisms reached the earth, and the surviving microorganisms became our ancestors.

Can microorganisms endure long-term space travel?

Kashbink's script seems very reasonable. , However, there are three conditions for this script to be established.

The first is the "travel time" problem of meteorites arriving on the earth.

The second is the "radiation" problem of flying in space.

The third problem is the meteorites entering the earth. The "heat" problem when in the atmosphere.

First, let's consider the "travel time". If it is too long, even microorganisms will die on the way. Professor Brett Gladman of the University of British Columbia calculated the travel time. .

"You might be surprised that a stone came to Earth from Mars in the first place. Because in the vast universe, the earth is just a small existence. ”

Mr. Gladman used a computer to calculate how long it would take to travel in space to reach the Earth. When an asteroid hits Mars, the debris will fly out in all directions, but depending on the direction of the flight and the position of the Earth, it will not reach the Earth. The Earth's movement time changes.

Calculations show that if a piece of debris is shot into space at a speed of 3.3 kilometers per second, about 1% of the debris will reach the Earth within a million years, and 0.1% of the debris will reach the Earth within 100,000 years. To reach Earth, 0.00001% of the debris will reach Earth within 10 years.

"A large impact can sometimes eject billions of fragments, so even under 10-year conditions, a dozen fragments will reach Earth. You might be surprised at how short the travel time is, but that's a natural consequence of the sheer amount of debris being ejected.

The travel time it would take for a meteorite to reach Earth doesn't seem that difficult to achieve.

Could there be organisms that are not affected by radiation?

What about the second scenario, space radiation?

What about microbes living in rocks? Cosmic radiation is also a major threat because of its high energy content and ability to penetrate into rocks. Can microorganisms survive radiation?

Utilized Kazunari Narumi of the Japan Atomic Energy Agency (JAEA) Takasaki Advanced Radiation Research Institute. Bacteria tested this problem.

Radioactive bacteria are known to be strongly resistant to radiation. Narumi placed 10 million pieces of DNA and E. coli in petri dishes and exposed them. Under high-energy radiation, the so-called heavy particle radiation, the result is that E. coli is killed, but the DNA bacteria survive and reproduce. From this experiment, it is believed that DNA can survive in the universe. Survive radiation for 10 years.

Why can DNA survive high-energy radiation? This is because the bacterium has a protein that speeds up DNA repair. This means that even if the DNA's double helix is ​​completely severed by radiation, it can still be repaired and survive.

It seems that the radiation problem that can be seen everywhere in the universe can also be solved.

Evidence left on meteorites flying from Mars

But in the end, a big problem was left, which is the problem of "heat" exposed when rocks enter the earth's atmosphere.

The surface temperature of the meteorite reaches thousands of degrees Celsius when it falls from the atmosphere. Can microorganisms break through this limiting condition?

Mr. Kashbink decided to test this question using meteorites that actually came from Mars. A meteorite found in Antarctica called ALH84001 was used for this purpose.

This meteorite crystallized in the magma pile of Mars 4 billion years ago and flew to the earth. Kashbink used a "magnetic microscope" that can measure the rock's tiny magnetic field to investigate whether the meteorite was heated at high temperatures from the meteorite's magnetic field.

Past heat data can be known from the magnetic field. When the rock cools and solidifies, the data records the direction of the meteorite's magnetic field. In addition, distortions in shape due to changes in the earth's crust are also recorded in meteorites.

Cashbink investigated some larger Martian meteorites and found that parts of the magnetic field near the surface of the meteorite were unevenly oriented and uneven. The magnetic field is reset, which is the part that has experienced high heat.

On the other hand, on the inside of the meteorite, the direction of the magnetic field remains uniform. This indicates that the magnetic field is not reset.

"When the meteorite passed through the Earth's atmosphere, it was strongly heated, eliminating the magnetic field about 3 mm on the outside. In other words, the heat only reached there. The inside above 3 mm was not heated to a very high temperature."

further investigated The temperature at which magnetic field reset occurs, turns out to be 40°C. In other words, the inner side of the meteorite where the original magnetic field remains is kept below 40°C.

"If it is within 40℃, not to mention bacteria, but also animal eggs can survive. Our ancestors came to the earth in such spaceships."

Microorganisms can travel in space

It seems that microorganisms Can survive the high temperatures of entering the atmosphere. Life on Mars came to Earth through meteorites and became our ancestors. Kashbink's theory is becoming more and more plausible.

Today, Mars is an extremely cold desert. But 4 billion years ago, people discovered that Mars was a planet more suitable for life than the Earth, with oceans and land.

Is Mars really the home of all life? The challenge for scientists to discover the origins of life will continue.