Mars Express -

The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) is a ground-penetrating radar. Using a 40-meter long boom antenna, it sends low-frequency radio waves toward the planet. Most waves reflect off the surface, but some penetrate the ground. By analyzing the returning echoes, MARSIS can "see" up to 3.8 kilometers below the surface. strong evidence of a 20-kilometer-wide liquid water lake buried beneath 1.5 kilometers of solid ice at the Martian south pole. This finding reignited the debate about whether Mars could still harbor microbial life today.

The name "Express" was derived not from the speed of its travel—though its six-month journey was indeed efficient—but from the rapid and streamlined design and build process. Engineers repurposed hardware and designs from the failed Mars 96 mission and ESA’s Rosetta comet chaser. This ingenuity allowed the mission to move from drawing board to launchpad in record time. Mars Express

ESA - Mars Express milestones: two-year mission enters third decade The Mars Advanced Radar for Subsurface and Ionosphere

Unwilling to abandon their investments and scientific goals, European planetary scientists proposed a rapid-recovery mission. This led to the creation of Mars Express, named for the unprecedented speed with which it was designed, built, and prepared for launch. By analyzing the returning echoes, MARSIS can "see" up to 3

: Close flybys of Mars' largest moon allowed scientists to measure its mass and density, suggesting that Phobos is not a solid rock but rather a highly porous "rubble pile" that resembles a sponge. Localised Aurorae : Mars Express found that Mars has localized aurorae