Astronomers have detected hydrogen peroxide (H2O2) in the atmosphere of Mars
for the first time. This is the first time that a chemical catalyst of this
sort has been found in a planetary atmosphere other than the Earth’s.
Catalysts control the reactions of the most important chemical cycles in the
Earth’s atmosphere. The result shows that scientists’ knowledge of the
Earth’s atmosphere can be used to explain the chemistry of atmospheres on
other planets, and vice versa. The work is announced in the March issue of
the journal "Icarus". The observations were made at the James Clerk Maxwell
Telescope (JCMT), situated near the 14000-ft summit of Mauna Kea in Hawaii.

Dr Todd Clancy, at the Space Science Institute (SSI) in Boulder, Colorado,
led the research team. He says "Mars is one of three observable terrestrial
atmospheres. Unlike Venus, Mars is hospitable enough to be considered a
possible human habitat in the future. And unlike the Earth, Mars is not
extensively explored and so presents an opportunity to discover new and
exciting phenomena."

Dr Brad Sandor, also at SSI, explains "We took advantage of the excellent
2003 opposition of Mars, when the Earth and Mars passed close by each other
in their orbits around the sun, to measure Martian atmospheric H2O2 for the
first time."

The Earth’s atmosphere has been studied much more than that of Mars.
Scientists have had to rely on their terrestrial experience to guess how the
Martian atmosphere reacts to solar radiation, and how its overall
photochemical balance is controlled.

Models predicted that hydrogen peroxide was the key catalytic chemical that
controls Mars atmospheric chemistry. Until now, scientists were unable to
detect the predicted amount of H2O2, so some researchers argued that the
models were wrong.

However, the new measurements of hydrogen peroxide made with the JCMT agree
with the predictions of standard photochemistry. Dr Clancy continues "We
have largely confirmed that the chemical balance of the Mars atmosphere is
determined by the products of the photolysis of water vapor, without the
need for special or unknown changes to current theory."

Dr Gerald Moriarty-Schieven of the National Research Council of Canada
worked on the project with Dr Clancy and Dr Sandor, and is based at the
Joint Astronomy Centre in Hawaii, which operates the JCMT. He explains more
about the JCMT observations: "The 2003 opposition was especially favorable
since it occurred when Mars was closest to the sun in its orbit, and hence
unusually close to us as we passed by. Mars was at its warmest, when the
most H2O2 is available to observe, and the JCMT can make especially
sensitive H2O2 measurements."

What impact does this result have for the search for life on Mars? Dr Clancy
says "Hydrogen peroxide is actually used as an antiseptic here on Earth, and
so it would tend to retard any biological activity on the surface on Mars.
For this reason, as well as the ultraviolet radiation and lack of water,
bacteria-like organisms are not expected to be viable on the surface. Most
arguments for finding life on Mars now center on subsurface regions."

Images

[Image]

Photograph of the James Clerk Maxwell Telescope, atop Mauna Kea on the Big
Island of Hawaii. CREDIT: Nik Szymanek.

* http://outreach.jach.hawaii.edu/pressroom/2004-marsperoxide/jcmt1.jpg
(full size JPEG 744kB)

* http://outreach.jach.hawaii.edu/pressroom/2004-marsperoxide/jcmt1-small.jpg
(smaller size JPEG 36kB)

[Image]

Photograph of the James Clerk Maxwell Telescope, atop Mauna Kea on the Big
Island of Hawaii. CREDIT: Nik Szymanek.

* http://outreach.jach.hawaii.edu/pressroom/2004-marsperoxide/jcmt2.jpg
(full size JPEG 240kB)

* http://outreach.jach.hawaii.edu/pressroom/2004-marsperoxide/jcmt2-small.jpg
(smaller size JPEG 24kB)

[Image]

Image of Mars made with the Hubble Space Telescope during the 2003
opposition. The James Clerk Maxwell Telescope spectral observations of
hydrogen peroxide were made during the same period. CREDIT: J. Bell (Cornell
U.), M. Wolff (SSI), NASA, ESA.

* http://outreach.jach.hawaii.edu/pressroom/2004-marsperoxide/mars-hst.jpg
(full size JPEG 323kB)

* http://outreach.jach.hawaii.edu/pressroom/2004-marsperoxide/mars-hst-small.jpg
(smaller size JPEG 15kB)