Scientists believe that a large crater, which has been discovered on Mars, might have been a lake several billion years ago. A space vehicle, which NASA sent to explore Mars, has discovered layers of clay and carbonate minerals in the walls of this crater. These substances may form in the ground only after the contact with water.

This crater, which has received the name of McLaughlin, is one of Mars's largest craters. It is 92 kms wide and 2 kms deep. The space vehicle discovered no traces of washouts on the crater's walls, which means that, most likely, no water has ever come into the crater from outside. If the crater really was once full of water, this water has most likely penetrated from underground.

Mars is smaller than the Earth, and the gravity power on Mars is three times weaker than on the Earth. Thus, scientists suppose that if underground waters have once existed on Mars, the soil layers that contained water were thicker and more clay-like than they were on the Earth. These conditions are ideal for bacteria to appear, scientists say. It is not ruled out that there is still water under the crater's bottom and that bacteria still live there.

"The McLaughlin crater is an ideal place for scientists to examine the structure of Mars's soil," Russian scientist Evgeny Chernyakov says.

"The fact that there exists such a deep natural hollow on Mars allows scientists to examine Mars's soil without drilling artificial holes," Mr. Chernyakov says.

"This makes delivering the relevant equipment to Mars (which would have been very difficult and costly) unnecessary. Now, all that we need is to send a small device to Mars, which would "look" into this crater and take photographs or samples of the soil. From the ribs of the crater, we can rather easily take samples of the ground that would otherwise have been very hard to extract."

On the Earth, scientists have discovered bacteria in samples of ground that was extracted from the depth of 5 kms. They are quite capable of living so deep in the ground if there is water there. This fact makes it possible to suppose that bacteria may also live at the similar depth in the ground of Mars - again, if there is water there.

Some scientists even suppose that it is deep in the ground that life first appeared on the Earth. Millions of years ago, the Earth had a very thin atmosphere, and asteroids often hit the Earth's surface (now, they usually burn out in the atmosphere before reaching the Earth).

But bacteria that lived deep underground were quite safe from asteroids' hits. Besides, although there was no oxygen in the Earth's atmosphere at that time, the species of bacteria that lived then needed no oxygen at all.

"If we find bacteria - or more complicated living organisms - on Mars, this may help us to learn more about the origin of life on the Earth, because life on both planets probably appeared in similar conditions," biologist Elena Vorobyova from the Moscow State University says.

"Scientists suppose that Mars appeared simultaneously with the Earth," Ms. Vorobyova continues, "and initially, from the geological point of view and the point of view of atmosphere, the two planets developed in a similar way.

"Probably, life on Mars appeared approximately at the same time when it appeared on the Earth, and the forms of life on the two planets were very similar. Then, as a result of a certain catastrophe, the composition of Mars's atmosphere radically changed. Some species of bacteria probably survived, but, most likely, in the new conditions, they developed into different forms of life than on the Earth."

"Even if there is no life on Mars, by examining Mars, we may better understand what the conditions on the Earth were like when the Earth was young," Elena Vorobyova concludes.

Scientists suppose that the lake in the McLaughlin crater dried up about 3 bln 700 mln years ago. The minerals which form the walls of the crater were formed at the same time. Their age corresponds with the age of the oldest minerals that have been found on the Earth.

Scientists also suppose that the McLaughlin crater is not the only place on Mars where living organisms may be found. Moreover, the majority of scientists believe that it won't be necessary to dig deep into Mars's ground to find them.

Experiments in laboratories have shown that bacteria that live on the Earth are quite capable of living several dozen centimeters deep in a soil that is similar to that on Mars. Thus, probably, once we may learn sensational news that life really exists on Mars.

Source: Voice of Russia