When I was a young man with less than 500 million years ago, Mars suffered a catastrophe that hung its magnetic field, leave it exposed to strong solar winds and caused him to lose most of its atmosphere. This is the most plausible story for children on the planet, according to the latest findings of the rover Curiosity.
The conclusion is in two studies published today in the journal "Science" that reveal with unprecedented precision the composition of air on Mars.
Already suspected that the planet had lost air in the past, but by analyzing in detail the composition of different gases, scientists realized that the initial atmospheric erosion was much more abrupt than previously thought, and then it subsided.
After being born with a thick atmosphere with pressure hundreds of times larger than Earth, Mars quickly lost almost all its air and became, perhaps, like our planet. The erosion continued, however, and today the Martian air is so thin that its pressure is less than one hundredth of that on Earth's surface.
Scientists were able to deduct this loss history of atmosphere because the lighter atoms of a gas are concentrated at the top of the atmosphere, and the solar wind pushes them off the planet with greater ease. The proportion of argon gas to atomic weight 36 to 40 atomic weight of argon with, for example, was greater before the air erode.
Scientists still debate what may have caused this loss of atmosphere so sudden, and this must have to do with the planet's magnetic field, which depended on a flow of magma inside. If this magma has solidified, magnetism faded and left the planet exposed to the solar wind, which was strong at that time. Another possibility is to have a large impact destabilized the flow of magma.
For Paul Mahaffy, leader of one of the studies, impacts with asteroids and comets may have realized narrow down old Martian atmosphere.
Curiosity's mission is to investigate the possibility of Mars has had conditions favorable to life in the past, but it is not yet clear whether the history of early loss of the planet's atmosphere is good news or bad for it.
Certainly, it is not an obstacle, because at least for a while the atmospheric pressure of the planet was adequate to maintain liquid water, whose flow left signs on rocks. "The question is how long this lasted water," said Mahaffy Folha. "It is plausible that it has persisted a long time under an atmosphere not as heavy as the original."
Chris Webster, head of NASA's another study out today, was optimistic. Even the atmosphere of Mars has been reduced to one tenth of its original size at the beginning, says she would still have a reasonable value, and only over time have been shortened to the current value.
"There was a period in which the atmosphere of Mars was similar to ours, and there was liquid water," he says. "You have to take into account, of course, that the surface of Mars is very cruel, very ultraviolet radiation, but below the surface there is the possibility that there was a lot of ingredients necessary for life."
These mild conditions, however, would be with the days since the end of the magnetic field of Mars would continue to lose atmosphere and pressure.
In November, NASA will send a probe to Mars Maven, which will investigate the current rate of atmospheric loss.