A leaky instrument will delay launch of the Mars InSight lander by at least two years, NASA announced at a December 22 press conference. The probe was slated to head to Mars in March 2016 to study the planet’s interior and reveal how terrestrial worlds (including Earth) form. Hopes of an on-time launch were done in by a faulty seismometer, built by France’s national space agency, that can’t hold its vacuum seal. The next launch window is in 2018 due to the position of Earth and Mars in their orbits. In 2012 NASA chose InSight over other proposed missions to sail a boat on the seas of Saturn’s moon Titan and to hop across the surface of a comet.