subject: Earth could seed Titan with life posted: Sat, 18 Mar 2006 10:31:37 -0000
[Panspermia rears its beautiful head, http://www.panspermia.org has
all the details. My only comment here is that if 20 rocks *per
impact* hit another planet, and there's 9 planets in this system and
10 impacts per planet, that's a lot of material circulating. There
is absolutely no reason why rocks from other systems would be doing
anything different, and indeed there is absolutely no reason why some
of those rocks from other solar systems escaped their systems and
have now arrived in ours. With their microbes aboard. This may have
happened many times already, over the past 4.5 billion years. Again,
the sheer number of successful "deliveries" from a single impact
suggests this circulation is common and plentiful. - Stu]
Earth could seed Titan with life
By Paul Rincon
BBC News science reporter, Houston , Texas
Terrestrial rocks blown into space by asteroid impacts on Earth could
have taken life to Saturn's moon Titan, scientists have announced.
Earth microbes in these meteorites could have seeded the organic-rich
world with life, scientists believe.
They think the impact on Earth that killed off the dinosaurs could
have ejected enough material for some to reach far-off moons like
Titan.
Details were unveiled at a major science conference in Houston, US.
The theory of panspermia holds that life on planets like Earth and
Mars was seeded from space, perhaps hitching a ride on meteorites and
comets.
To get terrestrial, life-bearing rocks to escape the Earth's
atmosphere and reach space, an impact by an asteroid or comet between
10 and 50km is required. Only a handful of recorded strikes in
geological history fit the bill.
Million-year journey
One of them is the asteroid strike 65 million years ago, which
punched a crater between 160 and 240km wide in what is today the
Yucatan peninsula, Mexico.
Brett Gladman from the University of British Columbia (UBC) in
Vancouver and colleagues calculated that about 600 million fragments
from such an impact would escape from Earth into an orbit around the
Sun. Some of these would have escape velocities such that they could
get to Jupiter and Saturn in roughly a million years.
Using computer models, they plotted the behaviour of these fragments
once they were in orbit. From this, they calculated the expected
number that would hit certain moons of Jupiter and Saturn.
The principal targets they chose, Titan and Europa, are of
considerable interest to astrobiologists, the community of scientists
who study the habitability of other planetary bodies.
Titan is rich in organic compounds, which provide a potential energy
source for primitive life forms, Europa is thought to harbour a
liquid water ocean under its thick crust of ice.
Hitting at speed
Dr Gladman's team calculated that up to 20 terrestrial rocks from a
large impact on Earth would reach Titan. These would strike Titan's
upper atmosphere at 10-15 km/s. At this velocity, the cruise down to
the surface might be comfortable enough for microbes to survive the
journey.
But the news was more bleak for Europa. By contrast with the handful
that hit Titan, about 100 terrestrial meteoroids hit the icy moon.
But Jupiter's gravity boosts their speed such that they strike
Europa's surface at an average 25 km/s, with some hitting at 40 km/s.
Dr Gladman said other scientists had investigated the survival of
amino acids hitting a planetary surface at this speed and they were
"not good".
"It's frustrating if you're a microbe that's been wandering the
Universe for a million years to then die striking the surface of
Europa," Dr Gladman said.
Asked after his presentation by one scientist whether he thought
microbes would be able to survive Titan's freezing temperatures, Dr
Gladman answered: "That's for you people to decide, I'm just the
pizza delivery boy."
The UBC researcher gave his presentation at the astrobiology session
held at the Lunar and Planetary Science Conference in Houston, Texas.
search: