August 24, 2011
Planets May Be Swapping Life Forms Regularly
Computer models of asteroid impact debris from Earth to other planets show 100 times more particles end up on Mars than prior studies have shown. The highest-energy impact simulations show debris being flung into the planetary orbits and eventually finding its way to Jupiter. Two moons of which may be amenable to some forms of Earth-based life, BBC News is reporting.
Panspermia is a theory that occupies much of meteoritic research, primarily that the precursors to life, or living organisms themselves, may have been delivered by an impact on the early Earth. Equally, however, Earth impacts may throw up debris that could be loaded with microbes or small, hardy organisms like water bears - which have already demonstrated the ability to survive the harsh conditions of space.
Other simulations have tackled the probability that Earth impacts seeded life in the solar system, suggesting that Earth debris could even have made it to Saturn´s moon Titan.
Mauricio Reyes-Ruiz and his fellow researchers at the Universidad Nacional Autonoma de Mexico have posted their study on the collision probabilities of particles ejected from Earth with other nearby planets.
In addition to showing that particles ejected from Earth could reach Jupiter, simulations also showed that the number of particles ejected from Earth that collide with Mars is two orders of magnitude greater than previous studies have found, PhysOrg.com reports.
The researchers explain that both results have astrobiological significance, especially due to the evidence for life-sustaining environments on early Mars and on Jupiter´s moons Europa and Ganymede.
Researchers analyzed 10,242 particles with a minimum ejection velocity of 11.2 km/s (which is required to escape Earth´s orbit). Different impact events throughout Earth´s history have ejected particles with a wide range of velocities, with the maximum determined by the speed of the impactor as it hits Earth.
The simulated ejected particles were projected to orbit the solar system for 30,000 years, which is the maximum estimated survival time for biological material in space.
Particles ejected from Earth´s leading face along its direction of motion are statistically more likely and have a higher probability of colliding with the planets Mars and Jupiter. Particles ejected from the trailing face are more likely to impact Venus.
Overall, researchers noted, the probability of particles ejected from Earth colliding with another planet is very small. Further studies will be needed to investigate the velocity distribution of the ejected particles, along with simulations that use a greater number of ejected particles to estimate collision rates that have greater statistical significance.
The ultimate question is whether any ejecta will carry living cargo that can fulfill the panspermia hypothesis, but Dr. Steinn Sigurdsson, an astrophysicist at Pennsylvania State University says that evidence of the hardiness of life has already been found closer to home.
“There are viable bacterial spores that have been found that are 40 million years old on Earth - and we know they´re very hardened to radiation.”
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