A space oddity

It seems ExoMars could not escape the standard medley of indecision and confusion that has, unfortunately, become the norm for large space projects like this. It has resulted in years of delay and concept iterations, and a circus of planning and financing problems that continue to cause problems.

Despite all this, ExoMars is, without doubt, the most ambitious European-led space mission to date. While the project initially had heavy US involvement, the project is now partnered the Russian space agency, Roscosmos. Despite the US completely dominating Mars landings and rover exploration on the planet’s surface, could it be Europe (and Russia) that will be remembered in the history books with the ultimate accolade, ‘first to confirm life on another planet?’

“We are about to begin a new era of Mars exploration for Europe,” said Alvaro Gimenez, ESA director of science and robotic exploration. “It's been a long road for ExoMars to reach this point, but we are now ready to launch in the spring.”

The name ExoMars states its core mission, examine the exobiology of Mars. It wants to shed light on that fundamental question: is life possible elsewhere in this universe?

A suite of instruments, both on the surface of the Red Planet, as well as in orbit, will search for any and all kinds of ‘bio-signatures’ past and present. The array of equipment being deployed requires two separate launches, with the first scheduled for March this year.

This first mission will carry the ‘Trace Gas Orbiter’ or TGO. From an altitude of 400km, it will gaze down at the Martian surface and look for important trace gases such as methane, water vapour and nitrogen dioxide, which could represent signatures of active biological processes.

The TGO will also monitor seasonal climate changes in the atmosphere’s composition and temperature in order to create and refine Martian atmospheric models. Its instruments will also map the subsurface for hydrogen, to a depth of a metre. This could reveal deposits of water-ice hidden just below the surface, which, along with locations identified as sources of trace gases, could also influence the choice of landing site for further landers.

“Even though they make up less than 1% of the atmospheric inventory, they should provide key indicators to the nature of any active processes, helping us to determine just how ‘alive’ Mars may be today,” said Håkan Svedhem, an ESA project scientist. “TGO will also monitor seasonal changes in the composition and temperature of the atmosphere.”

Piggybacking on the TGO will be a small probe lander called, Schiaparelli. Reminiscent of the Beagle 2, the lander will remain static on the Martian surface once it has completed its troublesome descent.

Donato Amoroso, deputy CEO of contractor Thales Alenia Space, said: “The entry, descent and landing module for in situ exploration of Mars entails huge technological challenges.”

While it doesn’t have anywhere near the instrumentation of Beagle 2, it hopes to do the one thing that Beagle 2 didn’t, land in one piece. Mars has a reputation for destroying spacecraft and landers, and ESA does not want to travel all that way to suffer the same fate. Schiaparelli is essentially a dummy run to test the landing systems and protocols.

Schiaparelli will collect valuable data on the landing orientation, control during in descent and touchdown velocity as well as test some of the technologies being pioneered including the heat shield, the parachute system, a radar Doppler altimeter system, and crushable material for impact loads attenuation.

Schiaparelli will enter the Martian atmosphere at 21,000kph, before being decelerated with the aid of a parachute. Finally, it will use a thruster system to gently land it on the ground. An instrumentation package called COMARS+ will monitor the heat flux on the back cover of Schiaparelli as it passes through the atmosphere with a Descent Camera (DECA) recording images of the landing site as it approaches the surface.

If Schiaparelli survives, as it is expected to, it will be able to transmit signals and apply its small sensor suite to analyse the local environment, until the remainder of its batteries are used up. TGO, along with ESA’s Mars Express and NASA satellites already orbiting Mars, will relay data for the few days that Schiaparelli is expected to operate.

The surface payload is called DREAMS, standing for Dust Characterisation, Risk Assessment, and Environment Analyser on the Martian Surface. It consists of sensors to measure the wind speed and direction, humidity, pressure, atmospheric temperature close to the surface, the transparency of the atmosphere, and atmospheric electrification. The package will operate for between two to eight Martian days, known as sols.

Rover to follow

The follow up mission earmarked for 2018 is then set to cement Europe’s transition from remote observation to surface exploration of Mars. The mission will see a full sized 4tonne rover and stationary Russian surface science platform landed on surface, to begin a search for exobiology. The ExoMars rover is expected to travel several kilometres during its mission and will be able to drill below the surface for samples that it will be able to carry out analysis onboard.

The primary objective is to land the rover at a site with high potential for finding well-preserved organic material, particularly from the very early history of the planet. The rover will establish the physical and chemical properties of Martian samples, mainly from the subsurface, as underground samples are more likely to include biomarkers as the atmosphere offers little protection from radiation and photochemistry.

The drill is designed to extract samples from various depths, down to a maximum of 2m. It includes an infrared spectrometer to characterise the mineralogy in the borehole. Once collected, a sample is delivered to the rover’s analytical laboratory, which will perform mineralogical and chemistry determination investigations. Of special interest is the identification of organic substances.

“The surface science platform will serve as a long-lived stationary laboratory to monitor the local environment, which could include passing dust storms, lightning, and space weather effects,” said Jorge Vago, ESA’s ExoMars 2018 project scientist. “At the same time, the rover will travel several kilometres to search for traces of past life below the surface. It’s a very powerful combination of instruments.”

To get it there, the rover and surface platform will be integrated together in a carrier module that will be launched on a Russian Proton Heavy Lift rocket. A descent module will separate from the carrier shortly before reaching the Martian atmosphere. During the descent phase, a heat shield will protect the payload from the severe heat flux. Parachutes, thrusters, and a damping system will reduce the capsules speed, and allow a controlled landing on the surface.

After landing, the rover will disembark from the module via a ramp and is expected to carry out its search for at least one Earth year, enabling images of the landing site to be sent back to Earth, as well as data around climate.

In an age where you only have to ask Google for all the answers, it is exciting to see that exploration isn’t something once done by those in the history books, but is something that engineers are doing today. This is history in the making.