While scientists believe conditions suitable for life might exist on the
so-called “super-Earth” in the Gliese 581 system, it’s unlikely to be
transferred to other planets within that solar system.
“One of the big scientific questions is how did life get started and
how did it spread through the universe,” said Jay Melosh, distinguished
professor of earth and atmospheric sciences. “That question used to be
limited to just the Earth, but we now know in our solar system there is a lot
of exchange that takes place, and it’s quite possible life started on Mars and
came to Earth. There’s also been a great deal of discussion about the possible
spread of life in the universe from star to star.”
Moon rocks and Mars meteorites have been found on Earth, which led Melosh to
previously suggest living microbes could be exchanged among planets in a
A Purdue University research team has found that,
in contrast to our own solar system, the exchange of living microbes between
“super-Earth” and planets in that solar system is not likely to
Laci Brock, a student studying interdisciplinary physics and planetary
science, and Melosh will present those findings at the 43rd Lunar and Planetary
Science Conference in The Woodlands, Texas.
Brock examined the Gliese 581 planetary system because Planet d, known as
super-Earth, falls in a “habitable zone” where liquid water could
“Laci has found the somewhat surprising result that it is very
difficult for materials to spread throughout that system in the same way it
could take place in our solar system,” Melosh said.
All four planets found in Gliese 581 are within close proximity to their
central star, which results in large orbital velocities, Brock said. However,
the initial velocity of material leaving Planet d is not enough to allow
exchanges among planets.
“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,” Brock said.
“It really shows us how unique our solar system is.”
Melosh said a more extended solar system would be needed for exchange of
materials among planets.
“None of the solar systems that have been found so far would have opportunities
for exchange of life among the different planets like what our own solar system
offers,” he said.
The Opik-Arnold method was used to simulate 10,000 particles being ejected
from Planet e and super-Earth. The velocity ranges of the particles were scaled
from each of the planet’s orbital velocities, which is very high by solar
system standards due to the close proximity to their central star.
“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,” Brock said.
Several members of Purdue’s planetary sciences department are attending the
43rd Lunar and Planetary Science Conference, presenting research on possible
biologic contamination of Mars’ moon Phobos by microbes from the surface of
Mars; the formation of jets on comets; and gravity anomalies around large lunar
“Purdue has quite a showing of different people at this conference to
showcase their work,” Melosh said.