Artist's concept of Virtual Planetary
Laboratory
Recipe:
Take a rocky mass [about 12.8 thousand kilometers
(nearly 8 thousand miles) wide], add carbon
dioxide, water vapor and methane. Place in stable,
circular orbit, the same distance from a sunlike
star as the distance between Earth and the Sun.
Heat to an average of 10 degree Celsius (50
degrees Fahrenheit) for 1 billion years.
Over the next few years, scientists at NASA's
Jet Propulsion Laboratory plan to cook up a series
of planets based on recipes like the one above and
play around with the ingredients. But they won't
be using real materials -- it will all be done in
cyberspace. The ultimate goal is to simulate a
plausible range of habitable planets, and to find
out how they might appear to planet-finding
missions of the future.
Dr. Vikki Meadows is principal investigator of
the Virtual Planetary Laboratory, a project that
was selected as a new lead team for the NASA
Astrobiology Institute to create tools that will
simulate a diverse range of planets and life
forms.
Artist's concept of Earth-like
planet
The
Virtual Planetary Laboratory will marshal the best
supercomputers available, and a team of 28
researchers from disciplines as varied as
statistics and biology, to model a gallery of
planetary atmospheres. The team's findings will
directly influence the development of future space
missions such as Terrestrial Planet Finder, which
will look for habitable planets around other
stars.
"We're trying to build a terrestrial planet
inside a computer," Meadows says. "This will help
us determine what the signatures of life on an
extrasolar planet will look like, once we have the
technology to study them."
The closest planetary systems are many light
years away, but the faint light the planets emit,
if separated into its component frequencies, can
provide a wealth of information. By analyzing the
colors of radiation detected by Terrestrial Planet
Finder, astronomers can look for the signatures of
biological products. These "biosignatures" can
provide evidence that the environments on these
planets may be able to support life. But what will
these as-yet-unseen biosignatures look like?
Finding out is part of the challenge, and that's
where the Virtual Planetary Laboratory comes in.
Earth's biosignatures include methane,
liquid water, and ozone. If extraterrestrial
scientists observed Earth from far away and were
to detect these chemicals in large quantities,
they might conclude (correctly) that the planet
is inhabited.
Dr.
Cherilynn Morrow of the Space Telescope Science
Institute, a member of the team, says the Virtual
Planetary Laboratory will help scientists know how
to recognize habitable worlds and to discriminate
between planets with and without life.
"The Virtual Planet Laboratory is playing a key
role in defining how we will conduct our search
for living worlds in orbit around other stars of
the Milky Way galaxy," says Morrow, who heads the
project's education and public outreach component.
Currently, scientists are limited to just one
model of a habitable planet: Earth. The key to
expanding our concept of what constitutes a
habitable planet, Meadows says, is to play around
with the recipe, trying different combinations of
size, composition and location. A world teeming
with microbes, for example, could produce an
atmosphere rich in methane. And to learn about the
plausible range of temperatures at which life
might exist, "we'll model everything from frozen
hells to burning hells," Meadows says.
To help scientists recognize younger Earths,
the team will model our home planet as it would
have appeared from space billions of years ago,
before its atmosphere became rich in oxygen.
Artist's concept of Terrestrial Planet
Finder
An
equally important goal of the project is to learn
how to recognize what Meadows calls "false
positives" -- planets that may appear to have
life, but don't. These planets would mimic some of
the accepted signs of life, but would produce them
using geological and atmospheric processes. Such
planets might be distinguishable from inhabited
worlds by looking at a broader spectral range, or
taking many measurements over a period of time to
understand the way these "signatures" change.
In the first phase of the project, the software
will be used to re-create planets we're familiar
with: Venus, Earth and Mars. Comparing the models
with real data from observations of these planets
will tell scientists whether the software is
producing accurate simulations. Later stages will
produce abiotic, or non-living, planets, and
eventually, planets where life has found a
foothold.
Meadows stresses that she and her colleagues
aren't looking for "ET the Extraterrestrial."
Their sights are set on life on a lower order --
even microbial. "I'm not looking for intelligent
life," Meadows says. "I'm looking for bugs from
space."
November 4, 2002
Contacts: JPL/Randy Jackson (818)
393-5925
