Space

First ExoMars Mission Takes Off to Join Search for Alien Life

The Russian-European mission will place an orbiter around Mars to study trace gases in the atmosphere while a probe will try to land safely to validate tech that will be used to get down a rover in 2018.

Roscosmos's Proton rocket takes off with the Trace Gas Orbiter and Schiaparelli lander on March 14, 2016, from Baikonur, Kazakhstan. Credit: ESA

Roscosmos’s Proton rocket takes off with the Trace Gas Orbiter and Schiaparelli lander on March 14, 2016, from Baikonur, Kazakhstan. Credit: ESA

We’re going back to Mars again, this time in two parts with two space agencies teaming up. The European Space Agency and Russia’s Roscosmos have joined together to execute ExoMars, one half of which launched on March 14 from the Baikonur cosmodrome in Kazakhstan, on board Russia’s trusty Proton rocket. The craft will coast for seven months before reaching the red planet, on October 19. The primary objective of the mission is to find out if Mars has life or hosted life in the past. There are multiple other objectives, including demonstrating the technology that will prepare for future sample-return missions and human colonisation.

ExoMars 2016 consists of two modules: the Trace Gas Orbiter (TGO) and a lander called Schiaparelli. TGO will study the Martian atmosphere for methane and other trace gases that are indicative of biological processes. Schiaparelli will demonstrate landing capabilities (ESA’s and Russia’s previous landers failed), but won’t move around on the surface like a rover would.

TGO will orbit Mars after releasing Schiaparelli into freefall, and go on to map the blanket of gases surrounding the planet. It will pay particular attention to those present in trace amounts (less than 1% of the atmosphere), including methane, a key element of biological processes.

This hydrocarbon gas is interesting because of its association with biological processes. It is produced by microbial organisms called methanogens as they decompose biomass. An infamous source of methane on our planet is bovine flatulence (to use the technical term: cow farts); methanogens are present in plenty in the stomach of animals that ruminate or “chew the cud”. They’ve been present on our planet for over 3.5 billion years, since before oxygen showed up, since much before cyanobacteria, the species that burst forth filling our air with oxygen, came into the picture nearly a billion years later. Because Mars lacks oxygen but shows traces of methane, its environment is theoretically very similar to a primitive, pre-oxygenated Earth.

Then again, the gas is also produced by geological activity. Volcanism, for example, releases massive amounts of methane into the atmosphere. Igneous volcanic rock undergoes a transformation called metamorphosis on the sea floor, during interactions with Earth’s mantle or at tectonic plate boundaries, releasing methane. This process requires high temperatures and pressures, conditions that are found under the surface of Mars.  

Moreover, methane disappears from the atmosphere of a body in some 100 to 400 years because its molecules are broken down by ultraviolet radiation from the Sun. So if it is present in the atmosphere today, and is also present in pockets of strong abundance with seasonal variations, it has to have been supplied very recently or be replenished. TGO will help zero in on these sources and help determine if they’re geological or methanogenic processes. Both sources, if confirmed, would have tremendous impact on the study of Mars because the former would indicate an exciting geologically active world and the latter… well, aliens.

After dropping the Schiaparelli lander, TGO manoeuvre itself into an appropriately circular orbit for seven months, and commence full operations from May 2017. The orbiter has payloads built by Russia, Belgium and Switzerland, and is expected to function for another five or six years.

The lander is named after Giovanni Schiaparelli, who was born on the day of the ExoMars launch in 1835 and discovered surface features on Mars (including his observations of the optical illusions of lines he called canali, which became wildly but inaccurately infamous as ‘channels’ of liquid water). The eponymous contraption is a technology demonstrator. Its principal purpose is to land safely and prove that control descent of the sort it will exhibit actually works, and validate the technique’s use to land a rover in 2018. So, once released from TGO, Schiaparelli will slowly descend to a height of 120 km over four days, using two parachutes and orienting itself by hydrazine thrusters in short pulses.

Finally, it will descend to a height of two metres over the surface, hover for a few seconds, and then fall freely, with the final impact being absorbed by a crushable cushioning on its underside. The entire process, starting with the atmospheric entry and with a velocity of 21,000 km/hr to a final soft landing, will take less than six minutes. Scientists hope to land Schiaparelli in the thick of a sandstorm as well, studying the composition of Martian dust in the process. Then, it will survive for another four days before its weak battery runs out.

The landing site is called Meridiani Planum, a plain located just south of the planet’s equator. This site is of particular interest to scientists because it holds pockets of hematite, a mineral found abundantly near hot springs on Earth. There is evidence that the plain was flooded by water multiple times in the past; such a site could yet again be similar to conditions that existed on primitive Earth. Meridiani Planum was also the landing site of the Opportunity rover in 2004.  

Once on the surface, Schiaparelli will study the usual parameters of temperature, pressure, wind velocity, humidity, etc., in addition to measuring the weak and residual magnetic field around the planet.

Overview of Schiaparelli’s entry, descent and landing sequence on Mars, with approximate time, altitude and speed of key events indicated. Caption & credit: ESA/ATG medialab

Overview of Schiaparelli’s entry, descent and landing sequence on Mars, with approximate time, altitude and speed of key events indicated. Caption & credit: ESA/ATG medialab

ExoMars 2018, the second half of the mission, will contain a rover and a surface science platform. While the rover will move around freely, drilling and exploring a region within a radius of several kilometres from the as-yet undecided landing site, the surface platform will remain stationary, making measurements of subsurface water distribution and long-term climate change.

Sandhya Ramesh is a science writer focusing on astronomy and earth science.