Update, 26 November: The Mars InSight spacecraft has successfully landed on the red planet.
Earthlings are about to hear Mars’s heartbeat.
On 26 November, NASA’s InSight mission will attempt to touch down near the Martian equator. If it arrives safely, it will embark on the first mission dedicated to listening for seismic energy rippling through the red planet.
Any ‘marsquakes’ it detects could yield clues to the planet’s mysterious interior, including how it is separated into a core, mantle and crust. Whatever scientists learn about Mars’s innards could help illuminate how our own planet evolved billions of years ago.
InSight has been cruising through space since its launch in May, tracked by mission control at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. On Monday, at about 11:41 a.m. Pacific time, the spacecraft will rotate its heat shield forward to protect itself against the Martian atmosphere, which it will enter at nearly 20,000 kilometres per hour.
In a carefully choreographed sequence (see ‘Perilous journey’), the spacecraft will decelerate rapidly, heating it up to around 1,500 °C and exposing it to a force more than seven times stronger than gravity on Earth. InSight will deploy a parachute — one of the most crucial moments in its descent — extend its three legs, and, ideally, touch down at a gentle speed of just 8.7 kilometres per hour.
As it nears Mars’s surface, the spacecraft will test a new way to communicate with its controllers on Earth, 146 million kilometres away. Two ‘cubesats’, each the size of a briefcase, will attempt to talk with InSight and relay information from the craft to Earth in close to real time. If the experiment works, miniature satellites like these could allow faster communication with probes in deep space.
InSight’s landing sequence is nearly identical to that of NASA’s Phoenix spacecraft, which touched down safely near Mars’s north pole in 2008. The global dust storm that shrouded the planet earlier this year has abated, allowing for a clear path to the surface.
Mars scientists have been planning parties to watch the landing, with suitable snacks. Sabine Stanley, a planetary scientist at Johns Hopkins University in Baltimore, Maryland, says she may feature Mars bars or marzipan.
InSight is aimed at Elysium Planitia, a broad flat region that is just north of the Martian equator. It is one of the most boring places on the planet, says Bruce Banerdt, a planetary scientist at JPL and the US$994-million mission's principal investigator. That’s an advantage for InSight, which needs a safe, geologically stable place to do its work.
Mission scientists will use the lander’s camera to scout the ground for the flattest, least rocky area to deploy its French-built seismometer (see ‘Ear to the ground’). InSight’s robotic arm will pluck the instrument off its back and place it on the ground, then put a dome-shaped wind shield over it. The whole process is expected to take several days.
The instrument includes three ground-motion sensors nested inside a vacuum, and its sensitivity allows it to detect movement as small as the width of an atom. The big challenge will be determining which movements are caused by marsquakes and which are the result of jostling by the wind or other sources. On the third day after landing, project scientists will switch on an instrument to track changes in the magnetic field, which will help them identify sources of noise that aren’t quakes, says Catherine Johnson, a geophysicist at the University of British Columbia in Vancouver.
InSight’s German-built heat-flow probe won’t be deployed until January. Over the course of several weeks, it will drill five metres into the Martian surface, deeper than anything achieved before. Scientists will track changes in temperature as small as a few hundredths of a degree. That will tell them how much heat is leaving the planet, and how many heat-producing radioactive elements are packed inside Mars.
InSight is meant to work for a little more than one Martian year, or almost two Earth years. It should measure 50–100 marsquakes during that period, says Banerdt. The longer it survives, the more it will be able to detect — and the more researchers will be able to deduce about Mars’s internal structure.
Nature 563, 608-609 (2018)