Scientists have long studied the universe in a search for planets that could harbor life as we know it. Life as we know it requires water so scientists particularly study stars have planets orbiting within the habitable zone that could support liquid water. Some of these planets that have been discovered are dubbed super-earth because they can have up to 10 times the mass of our planet.
Some scientists believe that life on earth could have originated when microbes and other organic material inside meteorites from Mars impacted our planet. Those rocks could have been ejected from Mars by other impacts. However, on a super-Earth world such impacts may have a hard time ejecting any potentially life-harboring rocks from the surface due to needed velocities to reach other worlds in the system. Scientists have been analyzing the planetary system around Gliese 581, which is a red dwarf star with a mass about one third that of our Sun roughly 20 light-years from our solar system.
In the Gliese system, the planet Gliese 581d, which is the most distant planet in the system from its sun, falls in the habitable zone. Using computer models researchers simulated 10,000 rocks ejected off each planet in the Gliese system. The simulations found that the initial velocity of material leaving the system planet isn't enough to reach sister planets because the planets traveled much higher velocities. The findings also suggest that if one of the so-called super-earth planets developed intelligent life that was able to build spaceships, traveling to other planets in the system would be much more difficult than traveling around our own solar system.
"Ejections from planet 'd' have a low probability of impact on any other planet than itself, and most ejected particles would enter an initial hyperbolic orbit and be ejected from the planetary system," said study lead author Laci Brock, an undergraduate student at Purdue University. "Planet 'd' would have a very small chance of transferring material to the other planets in the Gliese system and, thus, is far more isolated, biologically, than the inner planets of our own solar system. It really shows us how unique our solar system is."