Atmospheric Study Shows Similarities in Sun's Effects on Earth and Mars

http://www.jhuapl.edu/newscenter/pre...06/060524c.asp

For Immediate Release
May 24, 2006

Media Contacts

Kristi Marren (The Johns Hopkins University Applied Physics Laboratory)
Phone: (240) 228-6268


Nancy Neal Jones (NASA Goddard Space Flight Center)
Phone: (301) 286-0039



Atmospheric Study Shows Similarities in Sun's Effects on Earth and Mars

First Definitive Example of Similar Solar Rotational Effects on
Planetary Atmospheres

"Despite differences in the chemical compositions and densities of
Earth's and Mars' atmospheres, we now have a definitive example showing
that both planets' atmospheres react similarly to varying levels of
solar energy impacting them during the sun's 25-day rotation," says
Elsayed Talaat, a space scientist with the Johns Hopkins University
Applied Physics Laboratory (APL) in Laurel, Md.

Talaat's findings, which will be presented in an AGU session
(Comparative Planetology: Atmospheres and Aeronomy I) on May 26 at
11:25
a.m., could help the atmospheric science community better understand
the
relationship between the sun and its effects on planetary atmospheres.

Comparing limited ionospheric data sets acquired in 2003 by NASA's Mars
Global Surveyor (MGS) and the agency's TIMED SEE instrument (Solar
Extreme Ultraviolet Experiment), Talaat says his findings provide
evidence that the photochemistry of Mars' ionosphere responds similarly
as Earth's to solar inputs.

"The upper atmospheres of both planets are impacted by varying levels
of
high-energy solar X-rays and extreme ultraviolet radiation during the
sun's rotation - the same type of data collected by the SEE
instrument,"
Talaat says. "I looked at the variation in solar irradiance found in
SEE's data and correlated that with the variability in Mars'
ionosphere."

To compensate for the sun's different rotational time periods as would
be perceived from Earth and Mars, he shifted SEE's data to match the
Mars timeframe. When two charts depicting the Mars peak ion density and
solar activity levels during a common timeframe were overlaid, the
plots
aligned.

The Mars ionospheric profiles were retrieved from the radio
transmissions from NASA's MGS Radio Science Experiment led by Dr. David
Hinson of Stanford University. Data are made available to researchers
worldwide via http://nova.stanford.edu/projects/mod/.

About TIMED
Since its launch in 2001, TIMED has been exploring one of Earth's last
atmospheric frontiers - the Mesosphere and Lower
Thermosphere/Ionosphere
(MLTI) - collecting valuable data during various phases of the solar
cycle. To date, TIMED and a worldwide network of ground-based
observation sites have collected unprecedented global observations of
the MLTI region's basic structure, temperature, pressure, wind and
chemical composition, as well as measurements of the region's energy
inputs and outputs. TIMED is the first mission to simultaneously
measure
all critical parameters so that scientists can better understand the
processes that control changes in the upper atmosphere.

TIMED is the first mission in NASA's Solar Terrestrial Probes Program,
and is part of the Heliophysics Great Observatory - a collection of
NASA's sun-Earth-focused missions. NASA Goddard's Solar Terrestrial
Probes Program Office, in Greenbelt, Md., oversees the mission,
sponsored by NASA's Science Mission Directorate, Washington, D.C. APL
built and now operates the spacecraft, leads the project's science
effort and manages the mission's Science Data Center for NASA.

For more information, visit http://www.timed.jhuapl.edu.

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The Applied Physics Laboratory (APL) is a not for profit laboratory and
division of The Johns Hopkins University. APL conducts research and
development primarily for national security and for nondefense projects
of national and global significance. APL is located midway between
Baltimore and Washington, D.C., in Laurel, Md. For information, visit
www.jhuapl.edu .