Leonid Meteors Yield Rich Astrobiology Research Results

Kathleen Burton

NASA Ames Research Center, Moffett Field, CA

650/604-1731, kburton@mail.arc.nasa.gov

RELEASE: 00-77AR

A team of NASA researchers and their collaborators report their findings
from last year’s Leonid meteor storm in today’s special issue of the
journal “Earth, Moon and Planets.”

The scientists – all members of the NASA and U.S. Air Force-sponsored
Leonid Multi-Instrument Aircraft Campaign – discussed their results in a
series of astrobiology-related papers in the peer-reviewed journal. While
their findings covered a range of areas, the key results reported have
implications for the existence and survival of life’s precursors in comet
materials that reach Earth.

“Last year’s Leonid meteor storm yielded rich research results for NASA
astrobiologists,” said Dr. Peter Jenniskens, a NASA astronomer based at
Ames Research Center and principal investigator for the airborne research
mission. “Findings to date indicate that the chemical precursors to life —
found in comet dust — may well have survived a plunge into early Earth’s
atmosphere.”

Jenniskens and his international cadre of researchers think that much of
the organic matter in comet dust somehow survived the rapid heating of
Earth’s atmospheric entry. “Organic molecules in the meteoroid didn’t seem
to burn up in the atmosphere,” he explained. They may have cooled rapidly
before breaking apart, he concluded.

Another manner in which organic matter can somehow survive the fiery plunge
into Earth’s atmosphere was discovered by a team from the Aerospace
Corporation, Los Angeles, who detected the fingerprint of complex organic
matter, identical to space-borne cometary dust, in the path of a bright
Leonid fireball. This “fingerprint” is still under investigation to ensure
that trace-air compounds are not contributing to the detection.

Another finding with potentially important implications for astrobiology is
that meteors are not as hot as researchers had previously believed. “We
discovered that most of the visible light of meteors comes from a warm wake
just behind the meteor, not from the hot meteoroid’s head,” said
Jenniskens. This warm wake has just the right temperature for the creation
of life’s chemical precursors, he said.

Utah State University researchers found that, during the meteors’ demise in
the atmosphere, their rapid spinning caused small fragments to be ejected
in all directions, quite far from the meteoroid’s head. This is an
important finding for astrobiology, because it means that meteors may be
able to chemically alter large amounts of atmosphere.

This year, the 2000 Leonid meteor shower is expected to peak twice — once
on Thursday night November 16 and again on Friday night November 17.
Although not as strong as last year’s storm, meteors will be visible across
the continental United States, with the East Coast predicted to provide the
best meteor viewing. Each night, optimal East Coast viewing will be at
approximately 2:50 a.m. (EST). West Coast observers can glimpse the showers
beginning after 11:00 p.m. (PST), and peaking between midnight and 1:30
a.m. Astronomers recommend that, because this year’s showers take place
during a last-quarter moon, optimal observing conditions demand a wide
field of view, with the moon behind trees or buildings.

An observing tool called the “Leonid MAC flux estimator” is available for
the general public at: http://leonid.arc.nasa.gov. It predicts how much
meteor activity is expected at a particular U.S. observing location.
Further images from 1999’s meteor storm, information about “Earth, Moon and
Planets” and other Leonids information can be found at:
http://amesnews.arc.nasa.gov

Astrobiology is the study of the origin, evolution, dissemination and
future of life in the universe. NASA’s Ames Research Center, in the heart
of California’s Silicon Valley, is the Center of Excellence for NASA’s
astrobiology research. It is also the location of the central offices of
the NASA Astrobiology Institute, an international research partnership –
among NASA and non-NASA agencies and institutions – to further astrobiology
research.