Emily LakdawallaApr 25, 2003

Scientists Detail Ambitious Goals of Mars Express

Scientists working on the European Space Agency's (ESA's) Mars Express detailed the mission's ambitious plan to study Mars from the top of its atmosphere to several kilometers beneath its surface, at a press conference in London, England last week.

Mars Express - which is scheduled to launch in early June and reach Mars by the end of December or early January 2004 -- will carry eight science instruments to perform its tasks of gathering data for what they hope will be at least one Martian year, or 687 Earth days. One of the eight instruments, the Beagle 2 lander, a spacecraft in its own right, will search for past or present life on the Martian surface.

With a little help from its friends

Despite the fact that its entire budget is one-tenth that of NASA, ESA has managed to mount the Mars Express mission by relying heavily on the legacy of previous space missions. The main body or "bus" of the spacecraft, for example, is based on the design of ESA flagship Rosetta, which is now slated to launch next year for Comet Churyumov-Gerasimenko or Comet Wirtanen.

In addition, a number of other instruments on board Mars Express are based on instrument designs developed for the Russian Mars 96 mission.

Prior to Mars Express, Mars 96, which was designed to study the Red Planet's surface, inner structure, atmosphere, and reactions to the solar wind, was probably the most ambitious planetary mission ever launched by any country. Unfortunately, the Russian spacecraft failed to reach escape velocity when it was launched in November 1996 and ended up in the ocean.
Model of Beagle 2

If all goes as planned, Mars Express and Beagle 2 will contribute to something of an unprecedented traffic jam at the Red Planet come January 2004. The mission will join the two American Mars Exploration Rovers and the Japanese orbiter, dubbed Nozomi -- along with the still-operating Mars Global Surveyor and 2001 Mars Odyssey orbiters -- in studying Mars concurrently.

Mars Express was originally scheduled to arrive at Mars on Dec. 26, 2003, but the necessary repair of a faulty component delayed the launch; consequently, the arrival, will now be delayed by several days. This scenario could result in communications headaches for the Beagle 2 lander, because the Mars Express orbiter will not be able to communicate with the lander for the first 10 days of its activities at Mars.

ESA has arranged with NASA to use Mars Odyssey as the communications relay for Beagle 2 during these critical first days of the mission. A delay in the arrival of Mars Express may mean that it will land very close to the landing date of the first Mars Exploration Rover spacecraft, which would claim a higher priority to critical communications time with Odyssey, if needed, than Beagle 2. However, once Mars Express has safely achieved its orbit, Beagle 2 will no longer have to rely on Odyssey, and the communications bottleneck will be vanquished.

Unlike NASA, ESA does not have the luxury of planning missions to Mars for every available launch window. (Launch windows open to Mars about every two years). Therefore, ESA has packed high hopes, along with its eight instruments, on Mars Express to achieve its objective of bringing home a significantly worthy scientific yield.

A true European collaboration

The science instruments, which have been contributed by England, France, Sweden, Germany and Italy, will investigate the Martian atmosphere, surface, and subsurface, shedding light on many aspects of Mars that have never before been studied from orbit. Four instruments are devoted to studying the Martian atmosphere:

ASPERA (Analyzer of Space Plasmas and Energetic Atoms), developed by Rickard Lundin and Stas Barabash with the Swedish Institute of Space Science, Kiruna, Sweden, will study how the solar wind interacts with Mars's atmosphere, looking specifically at the escape of volatile gases, particularly water, from Mars's atmosphere. This 'atmospheric escape' is one possible explanation for why there is so little water on the surface of Mars today.

MaRS (the Mars Radio Science experiment), overseen by Martin Päetzold, University of Cologne, Germany, will use the radio transmissions of the spacecraft to study the pressure and temperature within Mars' atmosphere, as well as the minute variations in the force of gravity across the Martian surface.

PFS (Planetary Fourier Spectrometer), developed in Italy and overseen by Vittorio Formisano, Instituto Fisica Spazio Interplanetario, Rome, Italy, will examine the composition of the Martian atmosphere with much greater accuracy than previous Mars missions.

SPICAM (Spectroscopic Investigation of the Characteristics of the Atmosphere of Mars) developed in France and overseen by Jean-Loup Bertaux, Service d'Aeronomie, Verrières-le-Buisson, France, is an atmospheric spectrometer that will concentrate on the question of what makes Mars's atmosphere so oxidizing. According to conventional Martian wisdom, oxidation is what has left the planet's surface rusty-red.

Two instruments will map the Martian surface:

HRSC (High/Super Resolution Stereo Color Imager) developed at DLR (Germany's Space Agency), is a high/super resolution stereo color camera that will provide the first, simultaneously captured, stereo images from Mars. It will photograph the entire planet in color at a resolution of 10 to 20 meters. HRSC can also capture super-resolution images at two meters per pixel, embedded within the frame of the lower resolution images.

OMEGA (Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activit) developed by Jean-Pierre Bibring, Institute d'Astrophysicque Spatiale, Orsay, France, is an infrared, mineralogical mapping spectrometer that will study the composition of the Martian surface and atmosphere by examining the wavelengths of infrared light reflected by different minerals and gases. It will map the whole planet at a resolution of two to five kilometers, and smaller areas at a resolution as high as 400 meters.

Both HRSC and OMEGA were originally developed for Mars 96.

One instrument -- MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) -- will for the first time directly study what is beneath Mars' surface, utilizing techniques similar to those used by oil geologists. MARSIS, a subsurface sounding radar/altimeter developed by Giovanni Picardi, Universita di Roma La Sapienza, Rome, Italy, is the first instrument of its kind ever flown on any planetary mission and may even address the enigma about the presence of liquid water.

The general consensus now among scientists who have studied Mars is that the planet still retains water somewhere and that much of it has seeped deep underground. MARSIS will use a 40-meter-long antenna to analyze reflections of radiowaves in the upper two or three kilometers of the Martian surface to reveal the depth below the surface to frozen and even, perhaps, wet soils.

Beagle 2 to search for life

The really big question that has long loomed over Mars however is the question of life - did it ever exist in any form back then - or now?

Not surprisingly, much attention has been focused on the Beagle 2 lander, developed under the auspices of Colin Pillenger (CK SP) at the Open University, United Kingdom. Beagle 2's mission is to explicitly look for evidence of life, past or present, on the surface of Mars.

Beagle 2 will be gently released and pushed ahead of the main spacecraft five days before Mars Express goes into orbit. It will enter the Martian atmosphere much like Pathfinder/Sojourner did and drop to an airbag-protected landing in Isidis Basin, where it will bring its own suite of eight instruments and tools to bear on the rocks and soils within reach of its one robotic arm.

The Gas Analysis Package (GAP), another first of its kind instrument, is designed to perform mass spectrometry and isotope analysis, in order to identify carbon-bearing materials in the rock. In addition, It will study the ratio of carbon-12 to carbon-13. Unusual carbon 12 / carbon 13 ratios in atmosphere or soil might be evidence for either past or present carbon-based life on Mars. GAP will also look for methane, a byproduct - and hence telltale clue of the presence of living creatures - in the atmosphere.

In addition to those studies, Beagle 2 will also investigate other elemental isotopes that could reveal the age of the Martian rocks. Two devices will collect the samples of rock and soil and deliver them to the GAP. A corer/grinder can drill into a rock and extract a fresh rock sample from beneath the rock's surface. Another device, known as PLUTO (Planetary Undersurface Tool) is a mechanical mole that can burrow beneath rocks and soil to grab soil samples from below the Martian surface. These areas beneath the surface are important to scientists because they may be hotbeds of microscopic life for the simple reason that the planet's ultraviolet light - which can be deadly to organic molecules - does not extend that deep.

Beagle 2 also carries a pair of stereo cameras, a microscopic imager, and two spectrometers for analyzing the tiniest details of structure and composition of Martian rocks and soils. Yet another suite of environmental sensors will study Mars's weather over its planned six-month mission.

Notably, the stereo camera has the same color filters as the camera aboard the Pathfinder mission, so that will allow scientists to directly compare images taken from the Beagle 2 and Pathfinder landing sites. Better still, the scientists have promised that these images from the stereo camera should be available to everyone soon after landing.

Once the Beagle 2 lander has unfolded its solar panels, it can pop up a little curved mirror that will allow one camera, which faces the sky until the robotic arm is deployed, to capture a view of the terrain immediately surrounding the spacecraft.

ESA wants to increase the science return from Mars Express by scheduling cooperative, simultaneous observations of the Martian surface and atmosphere by Beagle 2 and the orbiter. Agency officials also report that they hope to coordinate with the Japanese Nozomi spacecraft. Unlike Mars Express, this spacecraft is to be placed into an equatorial, rather than polar, orbit, so the two spacecraft will cross paths frequently throughout their mission lifetimes.

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