(CNN) Although it looks like a beautiful mound of snow on the Red Planet, the Korolev crater would be more suited for ice skating than building a snowman. The European Space Agency released an image taken by its Mars Express mission on Thursday, showing the crater filled with water ice.

But the crater isn't just icy because of the Martian winter. Korolev crater is filled with ice that's about 5,905 feet thick all year long.

The crater, which is nearly 50.1 miles across, is just south of the northern polar cap, known as Olympia Undae, in the northern lowlands. The deep base of the crater floor, about 1.2 miles below the rim, contains ice and acts as a cold trap. Air moving over the ice cools and sinks, creating a layer of cold air over the ice. This has enabled the ice to remain without melting.

The crater was named for Sergei Korolev, a chief rocket engineer and spacecraft designer known as the father of Soviet space technology. Korolev worked on the Sputnik program, the Vostok program that carried the first human into space in 1961 and rockets that were precursors to the Soyuz launcher.

The image itself is a composite of pictures of the crater taken by the Mars Express High Resolution Stereo Camera. The European Space Agency's Mars Express mission is celebrating 15 years after it launched in June 2003 and entered Martian orbit on December 25, 2003.

InSight places its first instrument

The work never stops for NASA's InSight mission . Since landing on the Martian surface on November 26, the lander has been taking photos and surveying its surroundings.

And on Wednesday, it placed its first instrument on the surface, the seismometer -- the first time a seismometer has been on the surface of another planet. The lander's robotic arm can reach about 5.3 feet, so the seismometer was placed at that distance in front of the lander.

Photos: NASA's InSight lander on Mars InSight recently captured an image of passing clouds on Mars. Hide Caption 1 of 10 Photos: NASA's InSight lander on Mars InSight's second selfie on Mars reveals dust on the lander. Hide Caption 2 of 10 Photos: NASA's InSight lander on Mars InSight placed the SEIS instrument, or seismometer, on the Martian surface on December 19. This is the first seismometer placed on another planet. Hide Caption 3 of 10 Photos: NASA's InSight lander on Mars InSight as seen from space. The craft, its heat shield and its parachute were imaged on December 6 and 11 by the HiRISE camera onboard NASA's Mars Reconnaissance Orbiter. Hide Caption 4 of 10 Photos: NASA's InSight lander on Mars This is NASA InSight's first selfie on Mars. It displays the lander's solar panels and deck. On top of the deck are its science instruments, weather sensor booms and UHF antenna. Hide Caption 5 of 10 Photos: NASA's InSight lander on Mars InSight took this image on November 26, 2018, as it was deploying its solar arrays. Hide Caption 6 of 10 Photos: NASA's InSight lander on Mars InSight's first image shortly after landing on the Martian surface on November 26, 2018.This was captured by the lander-mounted, Instrument Context Camera, with the dust shield still attached, to show the area in front of the lander. Hide Caption 7 of 10 Photos: NASA's InSight lander on Mars MarCO-B took this images as it approached Mars from about 357,300 miles away, just before InSight landed on Mars. Hide Caption 8 of 10 Photos: NASA's InSight lander on Mars This illustration shows the InSight lander as scientists and engineers first pictured how it would look on the Martian surface. Hide Caption 9 of 10 Photos: NASA's InSight lander on Mars This is one of the MarCO spacecraft that followed InSight to Mars, a suitcase-sized CubeSat that helped communicate the successful landing of InSight with NASA. Hide Caption 10 of 10

"Seismometer deployment is as important as landing InSight on Mars," InSight Principal Investigator Bruce Banerdt said in a statement. "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives."

It's known as SEIS, short for the Seismic Experiment for Interior Structure.

"InSight's timetable of activities on Mars has gone better than we hoped," InSight Project Manager Tom Hoffman said in a statement. "Getting the seismometer safely on the ground is an awesome Christmas present."

The seismometer will help scientists understand what's happening beneath the Martian surface, detecting "marsquakes" and analyzing seismic waves.

"Having the seismometer on the ground is like holding a phone up to your ear," said Philippe Lognonné, principal investigator of SEIS from Institut de Physique du Globe de Paris and Paris Diderot University, in a statement. "We're thrilled that we're now in the best position to listen to all the seismic waves from below Mars' surface and from its deep interior."

New data will start to arrive on Earth once the seismometer is level.

The Rotation and Interior Structure Experiment, or RISE, is active on the spacecraft, using a radio to track the wobble of the Martian north pole as the sun tugs on its orbit. This will provide more information about the planet's core. The heat probe will be hammered into the surface by the lander in late January.

The mission scientists are ready for the data that SEIS will send their way.

"We look forward to popping some Champagne when we start to get data from InSight's seismometer on the ground," Banerdt added. "I have a bottle ready for the occasion."