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Europe’s first space mission to Mars
In the nineteenth century, Charles Darwin made his historic journey in HMS Beagle to find the answer to the question about the overwhelming diversity of life on Earth. The journey resulted in his “theory of evolution by means of natural selection” that is routinely taught in biology today.
Now a Britain-led team of scientists has sent a mission to Mars, which will finally answer the question whether there is life on Mars or not. To honour Darwin’s scientific quest, this mission is named Beagle 2 and it is a part of “Mars Express” — Europe’s first mission to the Red Planet.
Launched on June 2 by a Soyuz-Fregat rocket from the Baikanour Cosmodrome in Kazakhstan, Mars Express is now cruising towards Mars with a speed of 11,000-km/hour — about nine times faster than the speed of sound in air.
It took only four years for European Space Agency (ESA) to design and complete it; and it cost less than 300 million Euros. By the standards of missions to Mars, this is the least expensive probe.
This year is special, because Mars lies a mere 56 million kilometres from Earth — the closest it has been for 60,000 years. So, every mission to Mars will consume less fuel and spend less time to accomplish the journey. If all goes well, Mars Express will enter its orbit around Mars on Dec 25, 2003. Once stabilized in the orbit, it will drop its “scientific payload” — Beagle 2 — that will descend to Martian surface. Using a parachute-and-airbag mechanism for safe landing, it will bounce off a few times before settling on a low-lying Martian plain, Isidis Planitia, in the northern hemisphere. Equipped with a sophisticated geological toolkit, Beagle 2 will look for evidence of past life trapped in Martian minerals.
Orbiting the planet, Mars Express will study the Martian environment. Using ground-penetrating radar, it will look for ice buried beneath the planet’s arid surface. Cameras will produce three-dimensional images of Martian topography while other instruments study the planet’s thin but active atmosphere.
The primary science mission of Beagle 2 lander will last 180 Martian days, or sols (a sol is about 37 minutes longer than an Earth day). Though it won’t be able to move around, but it will collect and analyze samples of Martian rocks and soil within a 75-cm radius. To do so, it will use a specially designed 2.5-kilogram robotic arm, known as “Position-Adjustable Workbench” (PAW).
PAW is a marvellous piece of engineering innovation. Several instruments of Beagle 2 are located on this robotic arm. Among them are rock corer and grinder, stereo cameras, optical microscope, Mossbauer spectrometer and mole. Other instruments, housed in the lander’s body, include communications, electronics and battery subsystems, supporting instrument electronics, environmental sensors and gas analysis package (GAP).
Top lid of the probe will gently remove to reveal all of these equipments. Then, like the petals of a flower, solar panels of the probe will open, one after another.
To appreciate the ingenuity behind the PAW, one must understand the functions of different instruments attached to this robotic arm. Besides the instruments mentioned above, it also include a brush, scoop, and wide-angle mirror. Discrete electronic interfaces between each instrument and the lander would have been complex to build and heavy as well, not to mention increase in cost. To get rid of this complexity, PAW uses a single interface with a Field-Programmable Gate Array (FPGA) that can reconfigure itself to match each instrument’s need.
With the help of two stereo cameras built on PAW, scientists will identify suitable soil and rock samples. First they will take a number of overlapping stereo images of the landing site. Received back on Earth, these images will be analyzed by a powerful computer to construct a three-dimensional (3-D) representation of the site — also known as digital elevation model. In turn, this 3-D model will be used to plan close-up experiments on rocks and soil. Stereo cameras are sensitive enough and require only 0.75 milliradian per pixel. Both of these cameras can focus from 1.2m to infinity, and one of them can observe objects as close as 10cm.
Largely based on an optical instrument designed for the cancelled Nasa 2001 Mars Lander, optical microscope is yet another important feature of PAW. Mars receives only 43 per cent as much sunlight as Earth does. So it’s too dim for microscopic observations. So the mocroscope will use 12 LEDs (light emitting diodes) —three of them red, green and blue, and the three others ultraviolet. The red, green and blue LEDs will illuminate samples in sequence for a monochrome charged-coupled device (CCD) camera. Monochrome snapshots taken shall be superimposed to generate a final, colourful, microscopic image of the sample. UV LEDs will help identify bacterial life (or remnants of bacterial life) and some minerals. At a resolution of 4-8 micrometres, this microscope would not be able to identify individual bacteria but would detect bio-films (layers of certain organic compounds) produced by many bacterial colonies.
PAW is also equipped with a set of digging, drilling, and grinding tools to collect soil/rock samples. A subsurface soil sampler — planetary underground tool (named Pluto) — will dig to a depth of about 2 metres. The key component of Pluto is Mole - a soil penetrator and sampler. Invented by a Hong Kong dentist and precision toolmaker, Tze Chuen Ngnow, Mole is mounted in a metal tube and powered through a tether attached to Pluto.
Like a real mole, it can burrow into Martian soil or rock and get a 0.24 cubic centimetre sample. After crawling out at most three metres in any direction, the Mole can be reeled back into the PAW and positioned over a funnel to release its samples for analysis in the body of the Beagle 2.
In 1997, X-ray spectrometer of Mars Pathfinder Rover from NASA failed to positively identify rock samples through their coating of Martian dust. To avoid the recurrence of this failure, it was decided to include a grinder on Beagle 2. Any dust adhering to rock surfaces will be removed by the corer-grinder.
Its rotating bit can chop off a Martian rock to produce flat surfaces, each about 30mm in diameter. Then, PAWs built-in X-ray and Mossbauer spectrometers can be positioned to analyze the clean and tidy rock surface. It is important to note that corer-grinder on Beagle 2 can also sample the interior of rocks using a hammering and rotating action to get cores about half a centimetre long. No previous mission to the red planet has obtained a sample from within Martian rock.
Because the purpose of Beagle 2 is to conclusively answer the question of life on Mars, its every equipment is developed specifically to recognize the signatures of biological activities (whether extant or extinct). Gas analysis package (GAP) is just one of them. It is fine-tuned to detect lighter isotopes in samples of gaseous hydrogen, nitrogen, oxygen, and carbondioxide. It is designed on a principle that metabolic processes in every living being utilize lighter isotopes of the elements as compare to similar reactions involving no life. Such isotopic signatures of life can be found in four kinds of materials: organic carbon, carbonates, sulphates, and sulphides. Comparatively higher ratio of lighter elements in these compounds will point to the existence of life.
Over the intervals of temperatures, GAP will heat up samples to release gases that will then be passed into a mass spectrometer. An increase in lighter isotopes in the sample relative to the inorganic rocks would strengthen the case of life on Mars. By directly sampling the Martian atmosphere or by using samples gathered by subsurface soil sampler, GAP can measure quantities at nanogram (0.000,000,001 gram) scale.
Beagle 2 will also carry environmental sensors to measure UV radiation, temperature, atmospheric pressure, wind speed and direction, and the momentum and amount of atmospheric dust.
Subject to its success, Beagle 2 should enable us to say something with more confidence about life on Mars. With results from its multidisciplinary experiments in hand — hopefully by the next year — we’d have a firm standing on scientific grounds to suggest how common is life in the Universe. Can life take root any place with slightly favourable circumstances? Or does it need astoundingly sympathetic conditions similar to the ones in which we live.
The writer
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