InSight: A look inside Mars

5 May 2018

Illustration of InSight, within its cruise stage, approaching Mars.

The InSight mission, launched today from California's Vandenberg Air Force Base, is now on a six-month cruise to Mars. It is expected to arrive in November, but what will it find?

Mars may appear to be getting crowded, thanks to its growing robotic population, so why send another lander?

Illustrator and planetary scientist James Tuttle Keane takes us inside the Red Planet to explain why InSight is such a unique mission.

Set to land in Elysium Planitia, InSight will take up residence just north of the boundary between Mars' older, cratered southern highlands and northern lowland plains.

Also in the neighbourhood, not far to the south, is Gale Crater, where the Curiosity rover is currently exploring.

Illustration: InSight will measure seismic waves, which propagate through the subsurface after meteorite impacts. Mars has a crust and a mantle, but its core remains unknown. The Moon is shown to have a small inner and outer core, with Earth having a larger one.

James Tuttle Keane (Caltech)

Once landed, InSight will take over two months to deploy its instruments on the surface.

Gently lowered into place by a robot arm, its seismometer will investigate the planet's subsurface. SEIS will be able to detect the faint seismic signals of nearby meteorite impacts, which will reveal information about the interior structure of Mars, from the crust to the core. It will also be on the lookout for "Marsquakes", to see if the planet is geologically active.

Currently, scientists do not know whether the deep interior of Mars resembles Earth, with a solid inner core and a liquid outer core. Understanding this is one of InSight's key goals.

Seismology has been previously used to explore the interior structure of the Moon and Earth, with the Apollo astronauts measuring "Moonquakes."

Illustration showing a heat probe burrowing beneath the surface of Mars, with heat radiating out from the interior of the planet in red and yellow

James Tuttle Keane (Caltech)

InSight's heat probe, HP3, will burrow up to 5m beneath the surface to detect the amount of energy being released from the deep interior of the planet.

Measuring this heat flow will reveal whether Mars is composed of the same material as the Earth and Moon, and how the planet may have formed.

Illustration showing that Mars' spin axis is not perfectly perpendicular to the plane of its orbit around the sun. A molten core would cause the planet to have a greater wobble in its axis than a solid one.

James Tuttle Keane (Caltech)

The RISE experiment will enable scientists to precisely track InSight's location.

By bouncing radio signals back and forth between Earth and the lander, researchers will be able to use the Doppler effect to determine how much the planet's north pole wobbles as it travels around the Sun.

This wobble of Mars' spin axis can tell scientists about the core's size, and whether it is partially molten or solid.

Over the course of its 708 sol (728 Earth days) mission, InSight is expected to reveal the history of our closest Solar System neighbour as never before, right back to its formation about 4.6 billion years ago.