NASA's InSight lander has deployed its first instrument onto the surface of Mars, completing a major mission milestone that will allow scientists to peer into the Martian interior by studying ground motion -- also known as marsquakes, the US space agency said.
New images from the lander show the seismometer on the ground, its copper-coloured covering faintly illuminated in the Martian dusk, NASA said in a statement.
"InSight's timetable of activities on Mars has gone better than we hoped," said InSight Project Manager Tom Hoffman, who is based at NASA's Jet Propulsion Laboratory (JPL).
"Getting the seismometer safely on the ground is an awesome Christmas present," said Hoffman.
The InSight team has been working carefully towards deploying its two dedicated science instruments onto Martian soil since landing on Mars on November 26.
The Rotation and Interior Structure Experiment (RISE), which does not have its own separate instrument, has already begun using InSight's radio connection with Earth to collect preliminary data on the planet's core.
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Not enough time has elapsed for scientists to deduce what they want to know -- scientists estimate they might have some results starting in about a year, according to NASA.
To deploy the seismometer (also known as the Seismic Experiment for Interior Structure, or SEIS) and the heat probe (also known as the Heat Flow and Physical Properties Probe, or HP3), engineers first had to verify the robotic arm that picks up and places InSight's instruments onto the Martian surface was working properly.
Engineers tested the commands for the lander, making sure a model in the test bed at JPL deployed the instruments exactly as intended.
Scientists also had to analyse images of the Martian terrain around the lander to figure out the best places to deploy the instruments.
On December 18, InSight engineers sent up the commands to the spacecraft. On December 19, the seismometer was gently placed onto the ground directly in front of the lander, about as far away as the arm can reach -- 1.636 metres, away.
"Seismometer deployment is as important as landing InSight on Mars," said InSight Principal Investigator Bruce Banerdt, also based at JPL.
"The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives," Banerdt said.
The seismometer allows scientists to peer into the Martian interior by studying ground motion -- also known as marsquakes.
Each marsquake acts as a kind of flashbulb that illuminates the structure of the planet's interior.
By analysing how seismic waves pass through the layers of the planet, scientists can deduce the depth and composition of these layers.
"Having the seismometer on the ground is like holding a phone up to your ear," said Philippe Lognonne, principal investigator of SEIS from Institut de Physique du Globe de Paris (IPGP) and Paris Diderot University.
"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," Lognonne said.
In the coming days, the InSight team will work on levelling the seismometer, which is sitting on ground that is tilted 2 to 3 degrees.
The first seismometer science data should begin to flow back to Earth after the seismometer is in the right position, NASA said.