NASA's next mission to Mars, scheduled to launch next year, will focus on examining the deep interior of the red planet, according to the US space agency.
Information gathered by the Insight mission will boost understanding of how all rocky planets formed, including Earth, NASA said.
"Because the interior of Mars has churned much less than Earth's in the past three billion years, Mars likely preserves evidence about rocky planets' infancy better than our home planet does," said InSight Principal Investigator Bruce Banerdt of NASA's Jet Propulsion Laboratory (JPL) in California.
The mission will place a stationary lander near Mars' equator. With two solar panels that unfold like paper fans, the lander spans about six metres.
Within weeks after the landing, InSight will use a robotic arm to place its two main instruments directly and permanently onto the martian ground, an unprecedented set of activities on Mars, according to NASA.
One of the two instruments is a seismometer, which is shielded from wind, and has sensitivity fine enough to detect ground movements half the diameter of a hydrogen atom.
It will record seismic waves from "marsquakes" or meteor impacts that reveal information about the planet's interior layers.
The other instrument is a heat probe, designed to hammer itself to a depth of three metres or more and measure the amount of energy coming from the planet's deep interior.
A third experiment will use radio transmissions between Mars and Earth to assess perturbations in how Mars rotates on its axis, which are clues about the size of the planet's core.
Preparation ramped up this summer for the InSight mission which is on course for launch next May from Vandenberg Air Force Base in central California, NASA said.
"Our team resumed system-level integration and test activities last month," said Stu Spath, spacecraft programme manager at Lockheed Martin.
"The lander is completed and instruments have been integrated onto it so that we can complete the final spacecraft testing including acoustics, instrument deployments and thermal balance tests," Spath said.
The spacecraft's science payload also is on track for next year's launch, NASA said.
The mission's launch was originally planned for March 2016, but was called off due to a leak into a metal container designed to maintain near-vacuum conditions around the seismometer's main sensors.
A redesigned vacuum vessel for the instrument has been built and tested, then combined with the instrument's other components and tested again.
"We have fixed the problem we had two years ago, and we are eagerly preparing for launch," said InSight Project Manager Tom Hoffman, of JPL....