The probability of Panspermia
Microorganisms that crashed on Earth surrounded in distant body parts could have represent the seeds of life according to research by Princeton University, the University of Arizona and the Center for Astrobiology (CAB) of Spain.
The researchers reported that under certain conditions there is a high probability that life came to Earth in the Solar System childhood when our world and its planetary neighbors to exchange solid portions with other planetary systems that were close enough to share this material . This paper was presented on 25 September at the European Planetary Science Congress.
These findings provide support for the theory of "lithopanspermia" which is the idea that the basic forms of life are distributed throughout the universe through planetary fragments that have been ejected from the planets by volcanic eruptions, collisions, or other cataclysms. Over time, these fragments are trapped by the gravity of other planetary systems, making life that can transmit to other worlds.
The researchers suggest that the ideal conditions for lithopanspermia in the solar system and Earth overlap for several hundred million years (blue shaded area).
Previous research on this phenomenon suggested that the speed with which these fragments were ejected was insufficient to be trapped by the gravity of another solar system. But the new study has reconsidered the lithopanspermia under a process called weak transfer low speed, where objects can move from orbit to orbit a star other. In this mechanism, the minimum speed required would be around 100 kilometers per hour, ie about 50 times slower than previous estimates.
Scientists conducted simulations in the medium in which the Sun had birth the results were that the transfer of solid materials, among the stars in the cluster formation, it could have been a much more probable than previously thought. In fact, the new study indicates that between 5 and 12 in 10,000 small bodies in our solar system may have been captured from other solar systems.
This study suggests that lithopanspermia is a common process in the universe that could happen anywhere. The simulations also demonstrate that this transfer could result in the past in a time compatible with the emergence of life on Earth. The researchers reported that the Sun and its sister stars could have exchanged solids trillion before it became independent of our star in the star cluster was born, then these rocks were strong enough to survive interstellar travel and the environmental conditions.
"The conclusion of our work," said Moro-Martin, "is that the weak transfer mechanism makes lithopanspermia a viable hypothesis, since it would have allowed large quantities of solid material were swapped among planetary systems in scales time that could cause the survival of microorganisms embedded in large rocks. "
All of speeds
Previous studies pointed unlikely Transfer of solid material between different planetary systems.
In 2003, Jay Melos, published a document indicating that the probability that a meteorite ejected from Earth ended on another planet or another system was very small due to the enormous distances and speed that would require the body to reach that destination.
In 2005, David Spergel and Charles A. Young had another study indicating that it may be possible lithopanspermia when they were still young stars in the star cluster near where they were born. This probability increases with weak transfer theory.
The weak transfer occurs when a slow moving object, like a meteorite enters the outer edge of the zone of gravitational attraction of a larger body, with a relatively low speed, like a star or a massive planet like Jupiter.
Star clusters in formation satisfy two requirements for Transfer weak. First, the planetary systems that capture planets must contain solid matter traveling loosely bound by gravity to its star. Secondly, the planetary systems is exchanged between the material should have low relative speeds.
To estimate the actual amount of solid matter that could have been exchanged between the Sun and its nearest neighboring star, the researchers used data and models related to movement and the formation of asteroids in the Kuiper Belt and Oort cloud.
The researchers used these data to conclude that for a period of 10 to 90 million years, any solid object over 10 pounds could be transferring between the Sun and other stars, as well as between the planets of both systems.
But for that to happen lithopanspermia, first, microorganisms must survive the long journey with radiation. In 2009 he published a paper in the Astrophysical Journal that determined the time that microorganisms can survive in space depending on the size of the solid matter is hosted. Computer simulations showed that these times could be 12 million years for rocks of an inch in diameter, and 500 million years for an object of 2.67 meters wide.
Scientists estimated that under weak transfer, the solid matter that had escaped from a planet would need tens of millions of years to collide with another world. This would limit the planetary fragments weak to transfer at least one meter.
Adaptation of the theory with Life
According to the real possibility of transfer of life, scientists believe it could be given about 300 million lithopanspermia events in our solar system and in nearby planetary systems
But even if the organisms survive the journey to our planet, the Earth would have to be ready to receive them. Recent studies suggest that when Earth had only 288 million years, and there was water, so they could give an early life before the solar system met the 718 million years.
The Sun broke the stellar cluster in which was born approximately 135 to 535 million years, being able to give Transfer of bodies between stars to 700 million years after the formation of the Solar System.
Therefore, life arose on Earth shortly after count with water. There was a window of 400 million years that life could travel from Earth to other habitable worlds, and vice versa. If life is too early beginnings in other planetary systems is likely that life on our planet would have arisen in another world.
Researchers are trying to find out now the chances that in a world of terrestrial lithopanspermia. This does not mean that this is the theory of the origin of life on Earth, but indicates that it is an open possibility.