New Mars lander safely touches down. What happens now?

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After a 205-day journey through space, NASA’s InSight lander is safely on the surface of Mars. Tasked with peering beneath the Martian surface and mapping the planet’s underworld, InSight touched down just before 3 p.m. ET in a sunny patch of boring landscape inside the equatorial plains of Elysium Planitia.

Anxious teams of scientists and engineers, clustered together at the Jet Propulsion Laboratory in California, knew the spacecraft had survived its wild and tricky descent to the red planet’s surface after receiving data suggesting the lander had touched down safely-followed by an image from InSight itself showing a dusty, alien horizon with a single robot foot.

“This is what we really hoped and imagined in our mind’s eye,” says JPL’s Rob Manning, a systems engineer on the InSight team.

But the spacecraft’s home team isn’t fully celebrating just yet: For its mission to succeed, InSight must also deploy its solar panels, and that confirmation signal won’t arrive for a few more hours. But assuming it does, the spacecraft will officially be the newest member in an elite fleet of interplanetary robots currently exploring the red planet-including the Mars Reconnaissance Orbiter, which monitored InSight’s descent.

InSight’s journey of more than 300 million miles began on May 5 with a foggy, early morning launch from California’s Vandenberg Air Force Base. Tucked inside its shell, the spacecraft rocketed through the solar system, navigating by starlight as an onboard star tracker helped it stay on course.

On November 25 -and then once more, a few hours before touchdown-the spacecraft’s entry, descent, and landing team nudged it onto a trajectory that would allow it to bulls-eye in Elysium Planitia. This flat, unremarkable plain was chosen specifically because of the relatively abundant sunlight at the equator and its geologic boringness at the surface, which offers the best chance of finding ideal places to set down its instruments.

Once its plunge through the atmosphere was set, the team could only sit back and watch: Without guided entry, InSight had to fly itself to the Martian surface, meaning that a safe landing relied upon correct, preprogrammed commands and on all the necessary onboard instruments functioning properly.

“There are certainly points that will make me smile if they go well,” Julie Wertz-Chen, an entry, descent, and landing team member, said the week before.

As InSight made contact with the planet’s thin air, a heat shield protected it from burning up while it whizzed along at 12,300 miles an hour. About a minute later, the spacecraft deployed a parachute that put on a hefty brake and eventually slowed it to 134 miles an hour.

Its heat shield then popped off, and an on-board radar began to search for and ultimately lock onto the ground. At 3,280 feet up, InSight ditched its parachute, performed a short free fall, and then fired a dozen descent engines to eventually slow it to a mere five miles an hour.

From atmospheric contact to setting robot legs on the ground, the process took just 6 minutes and 45 seconds. Now, InSight is literally waiting for the dust to settle so it can start unfurling its solar panels.

InSight wasn’t the only robot entering Martian airspace for the first time today. Two mini-spacecraft, each about the size of a briefcase, were tagging along as part of the first mission to send tiny spacecraft known as CubeSats into interplanetary space.

Collectively known as Mars Cube One, but separately referred to as MaCO1 and MarCO2, their mission was to collect information from InSight as it descended to the surface, and then relay that information to mission control at JPL.

Now, it’s time for InSight to get to work. Over the course of one Martian year (or at least two Earth years), it will do something a bit different from most other Mars missions, which have focused on the planet’s flashy rift valleys, mammoth volcanoes, or signs of ancient running water on the surface.

Instead, this mission aims to get at the heart of Mars, to measure the size of the planet’s core and other interior layers. To do this, it will rely on marsquakes -or tremors that are often produced by the same tectonic activity that crafts those beautiful mountains and valleys.

One of InSight’s primary goals is to figure out how seismically active Mars is, says Renee Weber of NASA’s Marshall Space Flight Center.

“That is something that we don’t actually know,” she says. “That’s basically how many quakes there are, how often they occur, where do they occur, how big they are.”

Weber suspects that Mars will lie somewhere between Earth and moon in terms of tectonic activity (yes, the moon has moonquakes, which Apollo astronauts measured when they visited in the 1970s).

Parked on the surface, InSight is just waiting to snare those signals. Over the next three months, it will deploy its instruments, including an exquisitely sensitive seismometer that should detect a variety of marsquakes, both those produced by the planet’s own spasms and those resulting from meteor impacts.

After the spacecraft determines the location of a marsquake, it will read the incoming seismic waves and use the information they carry to figure out what types of rock they moved through. As marsquakes rock the planet’s innards, they send seismic waves bouncing through the interior, signals that travel just a tiny bit differently depending on what kind of material they’re moving through.

With enough data from enough different directions, scientists should be able to put together a picture of the planet’s alien heart. A second instrument will be deployed to take the planet’s temperature, drilling deep into Mars to find out how much heat is still escaping from its core.

All together, InSight’s readings will help scientists figure out how planets are put together and how they evolve, says Suzanne Smrekar, the mission’s deputy principal investigator. That’s important not only for better understanding our own solar system, but also for deciphering clues about much more distant planets circling other stars.

“Really understanding the whole enchilada, not just the surface,” Smrekar says, “is essential to really being able to make a reasonable prediction about what’s going on in these distant worlds.”