

If the ExoMars lander is successful, the risky touchdown procedure could become the strategy of choice for landing a new rover on the Red Planet.

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There has been a lot of talk about colonizing Mars lately, from Elon Musk's speech titled "Making Humans a Multiplanetary Species," to President Obama's op-ed this week called "America will take the giant leap to Mars." Its an exciting ultimate goal to put astronauts on Mars by the 2030s, but the next big step in Mars exploration is going to happen next week.

The European Space Agency (ESA) and Russia's Roscosmos have a stationary lander set to touch down on Mars on October 19. The Schiaparelli EDM lander (Entry, Descent and Landing Demonstrator Module) is part of ESA and Roscosmos's ExoMars mission to search for past and present Martian life, and the science team is hoping that it will be Europe's first successful Mars lander. (A British lander called Beagle 2 touched down on Mars in 2003, but communication was lost with the spacecraft during the final decent. It was discovered 12 years later that two of the spacecraft's solar panels failed to deploy, blocking the communication antenna.)

Graphic of the Schiaparelli EDM lander on Mars.
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Jorge Vago, an ESA ExoMars project scientist, told Sky & Telescope:

"The EDM is Europe's first try at landing on Mars, and as landing systems go, it is pretty ambitious. Schiaparelli incorporates a sophisticated Doppler radar to measure distance to the ground and speed over the surface. The information is used to command the pulsed hydrazine engines, which are organized in three clusters of three motors each."

Before firing the hydrazine engines, the Schiaparelli lander will deploy a parachute and use the thin Martian atmosphere to slow down as much as possible. The spacecraft also has a soft, deformable bottom that will buckle on landing to soften the impact, which should occur at about 10 km/h, or 6.2 mph. In this way, the landing is going to be similar to the Mars rovers Spirit and Opportunity, which used parachutes and then protective air bags for a high-speed landing.

The retro-rockets that the Schiaparelli lander will use to slow down further are similar to the Sky Crane that softly deposited the Curiosity rover on Mars. If the combination of all these technologies is successful, ESA will scale up the platform to land a rover on Mars in 2020, a European partner for NASA's Mars 2020 rover.

Schiaparelli EDM's descent sequence.
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Landing a spacecraft on Mars is no easy task. Just ask the aerospace engineers and physicists who have taken to calling the problem the "Great Galactic Ghoul," a fictional Martian beast that subsists on human spacecraft. Of all 15 attempted Mars landings, only 53 percent have been successful, and NASA is the only space agency that has completed fully successful landings on the Red Planet. (The Soviet Union's Mars 3 lander was a partial success, cutting out after just 14.5 seconds on the Martian surface.)

One spacecraft that has managed to evade the Great Galactic Ghoul for more than 12 years is NASA's Opportunity rover, which is still exploring Mars despite its original mission accounting for only 90 Martian days, or sols (92 Earth days). Opportunity happens to be investigating a gully near the Schiaparelli landing site, and the rover's science team is going to attempt to capture images of the lander's descent—something that has never been done before.

"We have asked the Opportunity team, and they will give it a go," Vago told Sky & Telescope. "However, it is not a given that we will get a nice image. Simulations show that if we arrive 'short' of the landing spot, we will be below Opportunity's observation horizon. Conversely, if we arrive 'long,' there is a better chance that the EDM and parachute may be imaged."

Schiaparelli will detach from the spacecraft that carried it to Mars, the ExoMars Trace Gas Orbiter (TGO), on Sunday October 16. The lander will then begin its three-day journey to the Martian surface as the TGO enters orbit around Mars to map the planet's atmosphere. Schiaparelli will enter that atmosphere on October 19 at and altitude of about 121 km (75 miles) and a speed of 21,000 km/h (13,000 mph).

The lander will use a front-end heat shield that will melt and partially vaporize before being jettisoned to protect the spacecraft's critical components from the extreme heat on entry. The parachute canopy will be deployed about 11 km (7 miles) above the surface, and the chute will be jettisoned just before hydrazine thrusters fire at a little more than a kilometer above the surface. The spacecraft will hover about 2 meters (6.5 feet) above the ground before cutting the thrusters and falling the rest of the way.

Diagram of the ExoMars Schiaparelli EDM lander.

Schiaparelli is primarily designed to test advanced landing systems, and the spacecraft is only expected to operate on the Martian surface for two to eight sols. Learning to stick the landing on Mars is crucial to future manned missions, however, because we are certainly not going to send astronauts into the domain of the Great Galactic Ghoul with only a 53 percent chance of mission success. With any luck, Opportunity will capture the whole thing, and we will have the first ever images of a Mars landing just seven days from now.

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