[meteorite-list] Could Life on Earth Have Come From Ceres?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 6 Mar 2009 18:01:23 -0800 (PST)
Message-ID: <200903070201.SAA11612_at_zagami.jpl.nasa.gov>

http://astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=3058&mode=thread&order=0&thold=0

Could Life on Earth Have Come From Ceres?
Astrobiology Magazine

Summary (Mar 05, 2009): The dwarf planet Ceres is rarely mentioned as a
candidate for habitability, but the possible presence of an ocean and
hydrothermal vents suggests it is plausible. If life developed on Ceres
long ago, could it have seeded the young Earth?

Could Life on Earth Have Come From Ceres?
By Lee Pullen

Astrobiologists hope to find life elsewhere in the universe, or possibly
even in our own cosmic neighborhood, the solar system. Their efforts are
usually concentrated on worlds such as the planet Mars, or icy moons
like Europa. However, there are other, less conventional locations in
the solar system where scientists think life may be found.

Ceres: an unusual choice

At the International Society for the Study of the Origin of Life
conference in Florence, Italy, Joop Houtkooper from the University of
Giessen divulged a theory that life could have originated on an object
in the asteroid belt named Ceres

Ceres was considered to be a planet when it was discovered in 1801, but
it was later downgraded to asteroid status. With the latest planet
definition from the International Astronomical Union, the round object
is now considered a dwarf planet. Is there a chance that this exotic
world is home to extraterrestrial organisms?

"This idea came to me when I heard a talk about all the satellites in
the solar system that consist of a large part of ice, much of which is
probably still in a liquid state," says Houtkooper. "The total volume of
all this water is something like 40 times greater than all the oceans on
Earth."

This reminded Houtkooper of a theory about how life originated.
Organisms may have first developed around hydrothermal vents,
which lie at the bottom of oceans and spew hot chemicals. Many icy
bodies in our solar system have rocky cores, so they may have had or
still have hydrothermal vents. Houtkooper realized, "if life is not
unique to the Earth and could exist elsewhere, then these icy bodies are
the places where life may have originated."

Looking at the evidence

Early in the history of the solar system was a period known as Late
Heavy Bombardment, a turbulent time when cataclysmic asteroid impacts
were common. If there was life on Earth before this dangerous era, it was
most likely eradicated and had to begin again after much of this cosmic
debris had cleared out of the inner solar system. Interestingly, evidence
indicates that Ceres avoided being pummelled by devastating impacts during
this time. If it had been bombarded, it would have completely and forever
lost its water mantle, as its gravitational force is too weak to
recapture it. This is probably what happened to the asteroid Vesta,
which has a very large impact crater and no water.

"The evidence points to Ceres having remained relatively unscathed
during the Late Heavy Bombardment," states Houtkooper. He says this
means Ceres still could have "a water ocean where life could have
originated early in the history of the solar system."

This leads to an interesting hypothesis. If the Earth was sterilized by
colossal impacts, but Ceres hosted life which survived, could the dwarf
planet have reseeded our world with life, via rock fragments that
chipped off Ceres and then crashed into Earth? Are all organisms on
Earth, including humans, descendants of Ceres? This is an idea that
Houtkooper had to pursue.

"I looked at the different solar system bodies which either had or
currently have oceans," he explains. "The planet Venus probably had an
ocean early in its history, but the planet's greater mass means that
more force is needed to chip off a piece of the planetary crust and
propel it in the direction of the Earth. Smaller objects like Ceres have
lower escape velocities, making it easier for parts of it to be separated."

Houtkooper then calculated the orbital paths of candidate planets, moons
and asteroids to see which were in the best positions to have pieces
successfully reach the Earth, without being intercepted by other
objects. Ceres fared favourably in these calculations.

Life on Ceres

Finally, Houtkooper considered the possibility of organisms still being
present on Ceres. "In the ocean, there could be life," he suggests. "On
the surface, it would be more difficult. But there are some
possibilities. There could be hydrogen peroxide-based life,
able to withstand the low temperatures." It's not currently known
whether hydrogen peroxide is present on Ceres, but nothing rules it out,
either.

The thought of Earth being seeded with life from Ceres and creatures
existing there today is certainly fascinating, but Houtkooper admits
that it is more science fiction than science fact until evidence can be
provided. This is naturally difficult to obtain, as Ceres is a small and
distant world. Even the best current images contain very little detail,
and just show that there are some surface features; what these features
are exactly is a mystery. Spectral analyses indicate the presence of
clay-like minerals, and Ceres? slightly flattened shape is what we would
expect from a world with a rocky core below a layer of water or ice.
Ceres is a dwarf planet with many secrets.

Fortunately, this will soon change thanks to NASA's DAWN mission.
Launched in 2007, the probe is due to arrive at Ceres in 2015. Once
there it will shed light on the mysterious world, and perhaps take
photographs of geysers of water erupting from the surface. Its close-up
view could indicate whether Ceres really does have the potential for life.

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Received on Fri 06 Mar 2009 09:01:23 PM PST