ExoMars: connect atmosphere, descent and subsurface science

ExoMars investigates whether Mars has supported life through complementary measurements. The 2016 mission carried the ExoMars Trace Gas Orbiter and Schiaparelli entry, descent and landing demonstrator. The orbiter reached Mars orbit, while Schiaparelli failed to land safely. Giving the entire program one success-or-failure label would conceal these different outcomes and the evidence each element returned.

The orbiter investigates trace atmospheric gases and provides communications relay capability. A detected gas can have more than one possible source, including geological and biological processes. Its abundance, location, variation and measurement uncertainty matter. A non-detection also has an instrument limit and observing context; it does not automatically prove that the substance is absent everywhere on Mars.

During Schiaparelli’s descent, unexpected rotation exceeded the inertial measurement unit’s measurement range. The resulting attitude-estimation error, combined with radar data, led the onboard system to calculate an impossible position below the surface. It released the parachute too soon and ended braking prematurely. The lander crashed, even though earlier entry stages and data collection had worked.

Relayed telemetry allowed investigators to reconstruct this chain. The engineering lesson concerns how sensors, models, software and validation interact, rather than simply blaming a parachute or declaring all data useless. In a fictional descent review, test the response to saturated measurements and inconsistent estimates, not just whether each sensor works in its normal range.

ExoMars: distinguish outcomes

The 2016 mission belonged to an ESA–Roscosmos partnership. After Russia’s invasion of Ukraine, ESA suspended the planned rover launch in March 2022 and ended that rover-mission cooperation in July. The redesigned Rosalind Franklin mission requires a European landing system and renewed international contributions, including NASA’s involvement. Those changes do not erase the earlier orbiter’s history.

The rover is designed to drill beneath the radiation-exposed surface and analyze samples in context. As described in ESA’s planning material, its launch target is 2028; that is a plan, not a completed landing. Even an organic molecule is not by itself proof of biology. Compare chemical evidence, environmental history, contamination controls and alternative explanations before making a life claim.