Mars is actually the most-studied planet in the solar system after Earth. In the last two decades alone, it has been under constant observation and study, yet we know very little about the Red Planet’s interior.
That should change from Monday, November 26th, 2018, when NASA’s latest mission to Mars, the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander touches down on Elysium Planitia.
The aim of the mission is to carry out a detailed examination of the Red Planet’s interior – its crust, mantle and core. Doing so can answer key questions about the early formation of the rocky planets in our inner solar system – Mercury, Venus, Earth, and Mars – more than 4 billion years ago. In addition, the data gathered may also help us to understand how rocky exoplanets orbiting other stars in our galaxy may have formed.
I’ve covered some of the more unique aspects of the mission in previous Space Sunday articles (see Insight on InSight, May 2018 and Mars Roundup, October 29th), including the use of two unique surface instruments, the Seismic Experiment for Interior Structure (SEIS) and HP3, the Heat Flow and Physical Properties Package to probe the planet’s interior. However, in order for the lander to use these, and its other instruments, it must conclude its 6-month journey to Mars with the Entry, Descent and Lander (EDL) phase – or as NASA mission engineers are calling it, 7 minutes of terror.
So-called since the 2012 landing of the Curiosity rover on Mars, it is known as such because by the time mission control receives the initial signals indicating the start of EDL, the Lander will be on the surface of Mars – in one piece or otherwise. These crucial seven minutes comprise (in the anticipated Earth Receive Time, when the signals are expected to reach NASA’s Jet Propulsion Laboratory):
- 19:47 GMT: encased in its aeroshell, InSight will enter the upper reaches of Mars’ discernible atmosphere 114 km (77 mi) above the surface of planet at 19,800 km/h (12,300 mph) at a critical 12-degree angle of attack. Any less than this, and it could bounce back into space, any greater and the heat generated by atmospheric entry could overwhelm the heat protection (designed to withstand temperature up to 1,500oC / 2,700oF, which is reached 2 minutes into the entry sequence), and burn-up the lander.
- 19:51 GMT: having been slowed to 1,400 km/h (860 mph) and at an altitude of 11 km (7 mi), the primary parachute is deployed. 15 seconds after this, the lower heat shield is jettisoned, and 10 second after that, the three landing legs are deployed.
- 19:52 GMT: ground sensing radar activates to measure the distance to the ground.
- 19:53:25 GMT: the lander separates from it aeroshell and parachute and the landing motors start firing as the lander orients itself for touchdown.
- 19:53:47 GMT: the motors reduce velocity from 27 km/h to 8 km/h (17 mph to 5 mph).
- 19:54 GMT: InSight touches down, with the motors immediately shutting down to avoid “bouncing” or toppling.
Depending on how systems check-out, the first image from InSight could be received by mission control about 8-10 minutes after landing – although equally, it could be received any time in the first 24 hours after landing. The Mars Odyssey orbiter should overfly the landing area at around 01:30 GMT on November 27th, and will hopefully be able to image InSight on the surface of Mars with its large, circular solar panels fully deployed – these will initially remain in their stowed configuration for around 20 minutes following landing to allow the dust thrown up by the lander’s motors to disperse and settle so that it doesn’t interfere with their operation.
Once settled on Mars, the primary mission, designed to run for a full Martian year, will commence – although it will be one that could take time to unfold.
InSight is kind of a laid-back, slow-motion mission. It’s going to take us probably two to three months, at least, to get our instruments down, and it could be early next spring before our principal instruments started returning data.
– InSight principal investigator Bruce Banerdt
As well as direct transmissions during EDL, NASA hopes to get real-time telemetry of the landing from a pair of cubesats, called Mars Cube One (MarCO), that launched as secondary payloads with InSight in May, and which will fly past Mars during the landing.
For those who wish to follow it, the InSight landing will be broadcast on a number of NASA on-line resources available.