The American space agency's InSight mission to Mars has begun to deploy its instruments.
The lander's robotic arm has just placed the bell-shaped seismometer package on the ground in front of it.
This suite of sensors, developed in France and the UK, will listen for "Marsquakes" in an effort to determine the internal structure of the Red Planet.
InSight touched down near the world's equator in November.
Whew – winding down after a long day, but I’ve done it: I’ve placed my seismometer on the surface of Mars! With SEIS, I’ll be able to listen in for marsquakes and help reveal the heartbeat of #Mars. https://t.co/GYNO4txPPi pic.twitter.com/18eQHXOfiO— NASA InSight (@NASAInSight) December 20, 2018
As well as the seismometer experiment, InSight is equipped with a heat probe that will burrow into the ground, and a very sensitive radio experiment that will measure how the planet wobbles on its axis.
Taken together, the probe's data should reveal the position and nature of all the rock layers below the surface of Mars - from the crust to the core.
It is information that can be compared and contrasted with Earth.
Full deployment of the instruments could take some weeks. The seismometer still needs its shroud placing on top.
This cover will protect the instrument's readings from noise introduced by the wind and temperature swings.