But the accompanying lander, Schiaparelli, crashed after a sensor error caused the spacecraft to jettison its parachute too early because it thought it was already on the ground instead of still two miles in the air.

The ExoMars rover, which will use a different landing system, was originally scheduled to launch in 2018, but that launch window was missed because of delays in the completion of the spacecraft and the instruments.

Some NASA Mars missions have also missed launch windows. Curiosity was to have launched in 2009 but was pushed back two years because of problems with electrical motors. Problems with a key instrument on Mars InSight delayed its launch to 2018 from 2016. Both eventually landed on Mars successfully.

The thin atmosphere of Mars makes landing particularly tricky, requiring careful testing of parachutes and other systems used to reach the surface. There is not enough air to provide much drag on the spacecraft as it speeds to the ground, although what’s there still generates friction that heats the exterior of a spacecraft to thousands of degrees.

Two earlier European landers — the Beagle 2 in 2003 and Schiaparelli in 2016 — failed. A number of Soviet landing attempts in the 1970s also failed. Only NASA has been able to successfully operate robotic spacecraft on the surface of Mars.

Last year, the parachutes for the ExoMars mission — one that is 50 feet wide to deploy at supersonic speeds in the Martian atmosphere, and a second, 120-foot-wide one that would billow out at subsonic speeds — failed in tests.

With NASA’s help, the problems with the ExoMars parachutes were diagnosed and additional tests are planned for this month.