ESA's Martian weather report (Forwarded)

ESA News
http://www.esa.int

14 January 2004

ESA's Martian weather report

Every day, people around the world tune in weather forecasts to plan their days
ahead. Soon ESA will be delivering the same service for Mars, thanks to an
ingenious experiment on board Mars Express.

Scientists around the world will be able to use this for some very special
planning of their own. The Mars Radio Science Experiment, or 'MaRS', is a very
special one on the European Mars Express spacecraft, which is now in its final
operational orbit around Mars. This experiment requires no additional hardware
-- only the main antenna that Mars Express uses to communicate with the Earth.

Yet it will provide the precise condition of the Martian atmosphere from ground
level up to an altitude of fifty kilometres. Included in these data will be a
measure of the ground air temperature of Mars to twice the accuracy usually seen
in weather reports on Earth!

To gain this information, scientists on Earth must transmit a precise signal to
Mars Express, which then sends it back, unchanged, once Mars Express has moved
close to the limb of Mars. Here the radio signal has to pass through the thin
atmosphere of Mars.

The temperature, density and pressure of the atmosphere cause subtle changes in
the signal that are detected on Earth and which, when analysed, allow the
scientists to see what the atmospheric conditions are on Mars.

Equally astonishing is that MaRS can detect minuscule variations in the movement
of Mars Express. Mars Express needs only to vary its expected motion by just
half the speed of a garden snail and this too will be detected by the MaRS
analysis software.

These movements are caused by the spacecraft passing over Martian features such
as mountains or the polar caps, whose masses cause tiny variations in the
gravitational pull on Mars Express compared to when the spacecraft is flying
over a flat plain or basin.

The data will be invaluable in determining the thickness of the planetary crust
and charting the seasonal variation in the carbon dioxide ice sheets that make
up the Martian polar caps.

"We aim to run the experiment for the next four years, providing a better
understanding than ever before of the daily and seasonal variations that occur
in the Martian atmosphere," says the MaRS Principal Investigator Martin Pätzold,
of Universität Koln.

Such data will allow planetary scientists on Earth to construct more accurate
computer programs to simulate or 'model' the behaviour of the Martian
atmospheric circulation. This ability could prove invaluable to future mission
planners, especially for those scientists contemplating landing sensitive
equipment, or even manned missions on the surface of Mars, perhaps as part of
ESA's proposed Aurora programme.

The first data from MaRS will be collected on 19 January. Although this
particular sweep will be treated as a test run, Pätzold hopes to be in
possession of his first Martian weather report this April.

More about ...

* Europe goes to Mars
http://www.esa.int/SPECIALS/Mars_Express/index.html
* Mars Express overview
http://www.esa.int/esaSC/120379_index_0_m.html

Related articles

* Orbiter instruments
http://www.esa.int/SPECIALS/Mars_Exp...C75V9ED_0.html
* Up where he belongs: An interview with Martin Pätzold
http://www.esa.int/esaSC/SEMZNOXLDMD_people_0_iv.html
* Chances of life are linked to water
http://www.esa.int/esaSC/SEMN3AR1VED_index_0.html
* Water on early Mars?
http://www.esa.int/SPECIALS/Mars_Exp...K75V9ED_0.html

Related links

* Institut für Geophysik und Meteorologie
http://www.uni-koeln.de/math-nat-fak.../prueford.html

IMAGE CAPTIONS:

[Image 1:
http://www.esa.int/export/SPECIALS/M...Q374OD_1.html]
Artist's impression of Mars.

Credits: Illustration by Medialab, ESA 2001

[Image 2:
http://www.esa.int/export/SPECIALS/M...html#subhead1]
MaRS (Mars Radio Science Experiment)will use the radio signals that convey data
and instructions between the spacecraft and Earth to probe the planet’s
ionosphere, atmosphere, surface and even interior. Information on the interior
will be gleaned from the planet’s gravity field, which will be calculated from
changes in the velocity of the spacecraft relative to Earth. Surface roughness
will be deduced from the way in which the radio waves are reflected from the
martian surface. "Variations in the gravitational field of Mars will cause
slight changes in the speed of the spacecraft relative to the ground station,
which can be measured with an accuracy of less than one tenth the speed of a
snail at full pace," says Martin Pätzold, MaRS PI from Köln University, Germany.

[Image 3:
http://www.esa.int/export/SPECIALS/M...html#subhead2]
Water may once have flowed freely on Mars and, like the Earth, the planet
receives sunlight and has its own internal energy source. So the odds on
primitive life thriving for at least some time during the planet’s history are
reasonably good.

Credits: Courtesy of Calvin J. Hamilton

[Image 4:
http://www.esa.int/export/SPECIALS/M...html#subhead3]
Martin Pätzold - Principal Investigator, Radio Science Experiment (MaRS) aboard
Mars Express.