Looking inside the Red Planet

THE latest NASA mission to Mars is on its way, with a successful launch last Saturday evening (Tasmanian time).

It is the InSight Mars lander, and it will hopefully reveal some new and muchhoped-for information about the interior of the Red Planet.

InSight will take about six and a half months to reach Mars, using the standard technique of what is called a transfer orbit. In order to minimise the energy needs to get to Mars, opportunities come about only once every two years, when the Earth and Mars are in the correct positions in their orbits.

To get to Mars, a craft is launched into an elliptical, or oval-shaped, orbit that is effectively part of an orbit around the sun, but reaching the orbit of Mars at the very time that Mars arrives at that location.

It is “coasting’’ to Mars, with the occasional necessary course correction to keep it exactly on target, just as when you drive a car you need to make small adjustments to the angle of the steering wheel even when on a straight road.

InSight will reach Mars on November 26 and, as always, the landing will be a dangerous part of the mission.

Travelling at more than 6km per second, InSight will use thrusters, parachutes and retro rockets to slow it down for a safe landing on the surface, at a Martian latitude of 4.5 degrees north of the equator.

It will, of course, send back pictures from the landing site, but I am not expecting that these will be particularly exciting. We are anticipating that InSight will land in a relatively flat plain devoid of spectacular features.

However, the lack of a photogenic landscape will not matter, because the mission is being sent to tell us more about what is under the Martian surface.

A key instrument on board the craft is the French-built Seismic Experiment for Interior Structure (SEIS), which will detect “Marsquakes’’. It is very sensitive: it can detect seismic movements in the ground even smaller than the size of a hydrogen atom.

It was this instrument that caused a delay in the original planned launch date. The SEIS needs to operate in a nearvacuum, but it was discovered to have a leak that could not be properly fixed in time for a 2016 launch. However, it’s fine now, and it is a beautifully designed instrument that can detect the source of the quakes just by making measurements from that one place on the Martian surface.

SEIS will measure both the primary and secondary waves from the quake, and these data will allow a determination of the location and magnitude of the Marsquake.

Of course, that helps in our knowledge of the interior of Mars, but there is another experiment that contributes to this knowledge. The Heat Flow and Physical Properties Probe, also called the HPPP, will drill to a depth of about five metres below the Martian surface, carrying temperature sensors to different depths. The idea is to measure the rate at which heat is reaching and escaping from the surface of the planet.

This will help researchers understand much more about the Martian interior and, in turn, is likely to assist with a general understanding about planetary formation.

It is increasingly important to carry out this research as we continue to discover planets in orbit around other stars, including planets whose mass and size are of the same order of magnitude as our Earth.

Currently, you can gaze at Mars yourself in the late evenings. If you watch low in the east after about 10pm, you will see a reddish-orange object almost as bright as the brightest stars. That’s Mars.

In about two and a half months, it will be closer to us than any time since 2003, and will be a very prominent object indeed.