NASA’s latest mission to another planet is set to blast off on Saturday on a seven month voyage across the frigid depths of space to Mars, with the aim of mapping the planet’s interior for the first time. The InSight mission aims to drop a lander the size of a garden table on to Elysium Planitia, a broad, flat and largely rockless lava plain on the Martian equator, from where it will become the first robotic probe to survey the centre of the red planet.
The region, which is so featureless it would normally make scientists glaze over, was chosen by NASA as the most suitable patch on the planet for the lander to set about revealing how Mars is arranged from the surface to core. “Where we land is an intentionally dull place,” said Neil Bowles, a planetary scientist at Oxford University, and one of some UK researchers involved in the mission. “It’s flat, empty and hopefully not very windy. And that is precisely what we need.” The lander has a suite of instruments to deploy once it reaches Mars. One, a spear-like heat flow probe, will hammer itself into the soil to measure how fast heat rises from the interior of the planet. Another is a seismometer that will be placed on the surface by the lander’s robotic arm. The instrument is so sensitive that it can detect vibrations smaller than the width of an atom. Hence the need for a smooth and quiet landing spot. By placing an ear to the ground on Mars, mission scientists hope to record tremors, or Mars-quakes, for the first time. Like other planets in the solar system, Mars is still cooling down from the heat of creation more than 4bn years ago. As heat radiates away from the surface, the crust contracts and buckles. With time, stresses build up and are suddenly released when vast stretches of rock slip past one another along geological fault lines, sending tremors through the planet.
Bruce Banerdt, the principal investigator on the mission at NASA’s Jet Propulsion Laboratory in California, said he expects InSight to record at least a dozen, but perhaps 100, Mars-quakes of magnitude 3.5 or stronger over the two-year mission. But scientists are hoping for more besides. From its landing spot near the equator, Insight should detect impacts from meteors that slam into Mars anywhere on its surface. Even the minuscule uplift of the ground caused by the gravitational pull of Mars’s moon, Phobos, should register on its instruments. More equipment on the lander will be used for a radio science experiment. Two antennas on the probe enable ground controllers to track the lander’s precise position on the Martian surface. With that information, scientists can monitor how much Mars wobbles on its axis, a movement that sheds light on the size of the planet’s core and whether it is liquid or solid.
With knowledge gleaned from the $814m (£600m) InSight mission – the name stands for “Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport,” scientists will gain a better understanding not only of how Mars formed, but how other rocky worlds assembled from primordial dust and debris. One mystery is why Mars, a planet less dense and half the width of Earth, did not grow any larger. “What we hope to do is make the first map of the inside of Mars, to map out its core, crust and mantle, and for the first time understand the structure of the interior,” said Banerdt. “We can then extrapolate that to Earth, Venus and even planets beyond the solar system.”
But before the mission can get to work, it has to get to Mars. The planet is never an easy destination, and only about 40% of missions from any space agency have been successful. For the scientists and engineers on the InSight mission, the journey will begin on Saturday at Vandenberg Air Force Base in California. Blast-off is scheduled for 4.05am local time (12.05pm UK). Riding on an Atlas V rocket, the InSight mission will swing around Earth before heading to Mars. Within two hours of launch, the spacecraft should make its first call home; the earliest confirmation scientists will have that the probe survived the rigours of launch. It will then be a long wait until InSight, flying with two briefcase-sized probes under test as communications links, arrives at the planet in November. Touchdown day is when things will get tense, said Banerdt. The spacecraft will tear into the Martian sky at 13,200 miles per hour, release a parachute, and then use 12 thrusters to slow its descent. “As soon as we’re down we’ll breathe more than a sigh of relief,” he said. “Once we’re on the ground and have communications set up, I’m confident we can get a lot of great science out of the mission, no matter what happens.”
Credit: Ian Sample for The Guardian, 4 May 2018.