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The InSight Lander, Looking Deep into the Red Planet

Posted on Fri, November 23, 2018
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  • After nearly seven months traveling through space, the latest US mission to Mars will land on the surface of Mars.
  • The InSight lander is designed to study the interior of Mars, with three instruments in its payload to collect data.
  • InSight is the latest in a history of NASA lander and rover missions that goes back to the 1970s.

On November 26 at around 3 pm EST, after nearly seven months traveling through space, the latest US mission to Mars will land (hopefully safe and sound) on the surface of the Red Planet. The InSight lander, designed to study the interior of Mars, is the latest in a history of NASA lander and rover missions that goes back to the 1970s. It follows in the venerable footsteps – or landing pads – of NASA’s first landers, the two Viking landers (1976) and the Mars Pathfinder lander (1997). Design-wise, it is very similar to two more recent landers: Mars Polar Lander (1999), which unfortunately crashed while attempting to land near the martian south pole, and the Phoenix lander (2008) that operated for more than a year on Mars.

Viking Lander Model

This photo shows a test version of the landers in the original "Mars Yard" built at NASA's Jet Propulsion Laboratory in 1975.

Landing on Mars is never easy. Mars has a very thin atmosphere, so conventional parachutes do not slow the spacecraft sufficiently on entry to provide a soft landing. However, the atmosphere is thick enough that a heat shield is needed to prevent the friction of reentry from burning up and melting the spacecraft. And for those landers like InSight that go directly from spaceflight to landing, they enter the martian atmosphere at supersonic speed. InSight will be traveling 13,000 mph when it reaches Mars. So, a heat shield and supersonic parachute just aren’t enough. InSight also has descent engines that will kick in about a mile above the surface to help it slow down before it lands, and then shut down immediately upon landing so the lander doesn’t bounce off of the surface and crash.

While previous landers and rovers and studied the rocks, soil, and weather of Mars, InSight is going deeper below the surface.

All of this means that there are multiple crucial steps that must happen just at the right time for the lander to touch down safely. An added challenge is that all of this has to happen automatically. An almost eight-minute delay in communication between Earth and Mars (Mars is currently about 86 million miles from Earth) makes it impossible to land the spacecraft by remote control.

InSight’s main focus will be the interior of Mars. While previous landers and rovers and studied the rocks, soil, and weather of Mars, InSight is going deeper below the surface. Among its instrument payload are three instruments designed to get under Mars’ skin.

Its primary instrument is a seismometer – the same technology used on Earth to detect earthquakes – called the Seismic Experiment for Interior Structure (SEIS). Studying the movement of seismic waves through a planet’s interior can reveal information about the planet’s core, mantle, and crust. Both Viking landers also carried seismometers, although only one of the seismometers deployed properly. The readings indicated that the planet had a crust between 14 and 18 km thick. The SEIS will be able to improve on these readings by several factors of accuracy.

InSight on Its Parachute (Illustration)

This illustration shows a simulated view of NASA's InSight lander descending towards the surface of Mars on its parachute.

Another instrument literally aimed at Mars’ interior is the Heat Flow and Physical Properties Package (HP3), which includes a probe nicknamed "the mole" that can penetrate as deep as 16 feet to study how heat flows inside Mars. These readings will help to determine the nature of Mars’ interior and how it has evolved over time.

A third instrument will be looking at the planet’s core less directly. The Rotation and Interior Structure Experiment (RISE) will use InSight’s communication system to provide precise measurements of Mars’ rotation and wobble. The communication signals traveling between the lander and the Deep Space Network on Earth allow scientists to track InSight’s exact location and velocity as it and the planet move through space. Scientists will use this data to calculate more precisely how much Mars wobbles on its axis. This data can then be used to determine the size and density of Mars’ core.

Data collected by previous orbiting missions indicated that Mars probably once had a large, liquid core (half the size of the planet), primarily made up of iron. This liquid core gave the planet a more extreme wobble than a planet like Earth, which has a solid iron inner core inside of a liquid outer core. Just how much of Mars’ core is still liquid is unknown – some evidence indicates that it has cooled and solidified completely. Continued study of the planet’s wobble may help to settle the issue.

Illustration of the InSight lander on the surface of Mars.

Illustration of the InSight lander on the surface of Mars. Credit: NASA/JPL-CalTech

InSight also carries multiple cameras to aid it in its mission. But you shouldn’t expect the types of breathtaking images the rovers Spirit, Opportunity, and Curiosity have sent back over the last 14 years of exploration. InSight’s landing site is in a relatively bland region called Elysium Planitia. Planitia is Latin for plain, and that’s what this region of Mars is. While just to its north is a large volcanic region, Elysium Planitia is a big, flat plain without much to look at. It’s a great place to land a spacecraft, and a great place to study the interior of Mars, but it’s not exactly postcard material.

If you want to tune in for the landing, it will occur around 3pm EST, 12pm PST. Join us at our Udvar-Hazy Center to watch the landing alongside Museum and NASA experts. And you can also check out a special episode of the Museum’s AirSpace Podcast dedicated to InSight and the exploration of Mars.

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