Mars Express

Agency

ESA

Country

🇪🇺 Europe (ESA Member States)

Launched

2003-06-02

Status

Ongoing

Mass

1,223 kg

Instruments

7 science instruments

HRSC stereo camera, OMEGA mineralogy mapper, MARSIS subsurface radar, PFS spectrometer, SPICAM UV/IR spectrometer, ASPERA plasma analyzer, MaRS radio science

Orbit

Highly elliptical polar orbit, 298 × 10,107 km, 6.72-hour period

Key Findings

1.MARSIS subsurface radar detected a 20 km wide subglacial liquid water lake under the south polar ice cap at ~1.5 km depth (published July 2018)
2.OMEGA identified phyllosilicates (clay minerals) and sulfates indicating early Mars hosted sustained liquid water for hundreds of millions of years
3.HRSC high-resolution stereo camera produced the first complete colour stereo map of the entire Martian surface
4.PFS spectrometer detected methane plumes in 2004 — a controversial finding that drove a decade of follow-on research

Mission Outcome

Mars Express, ESA's first planetary mission, has operated for over 22 years and continues to return science data as of 2026. Its detection of a possible subsurface liquid water lake is among the most significant Mars discoveries of the 21st century, though the interpretation remains debated. The spacecraft serves as a relay asset for ESA surface missions.

Sources

[1] ESA — retrieved 2026-06-01
“Mars Express has been orbiting the Red Planet since December 2003, contributing a wealth of data about the planet's atmosphere, surface, and subsurface.”
[2] NASA NSSDCA — retrieved 2026-06-01

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