Three days after a spectacularly successful landing on the surface of Mars, the InSight lander, packed with international science experiments, remains healthy as control teams on Earth gradually configure the lander for its two Earth-year primary scientific mission.
Configuring InSight for its primary mission:
Following a picture-perfect landing on Monday on Elysium Planitia on Mars, InSight’s control teams began slowly checking over the science platform’s health and activating some of its science experiments.
With a healthy lander, the meticulous process of preparing the platform and its robotic arm for deployment of its most important instruments and commencement of full-scale science operations is progressing slowly – as intended.
The goal of the InSight mission is not speed, and health checks and platform configurations are planned for a leisurely pace to ensure that everything is done correctly and nothing is over exerted.
Presently, InSight is starting the process of unlocking its robotic arm. The arm and platform’s cameras will be used to first assess the condition of the lander once arm movement operations begin.
Those cameras will also be used to assess the terrain in front of InSight for any hazards in the area that the lander’s seismic sensor and penetrating heat probe experiments will be deployed to on the Martian surface.
To accomplish the mission’s primary objectives, InSight carries a suite of three primary international scientific instruments that will allow the spacecraft to understand not only surface conditions and weather patterns on Mars but also its geologic interior – all of which will help us gain a better understanding of how Mars formed and how it transitioned from the warmer, watery planet of its past to its current arid state.
Seismic Experiment for Interior Structure:
Of the experiments that will look to the interior of Mars, the Seismic Experiment for Interior Structure, or SEIS, will – for the first time – seek to determine the presence of marsquakes and, if they are present, their intensity while also exploring how Mars’ crust is affected by the impact of meteorites.
Understanding the Mars crust’s reaction to seismic waves generated by meteorite impacts can help scientists better understand the Red Planet’s interior structure… as can measuring the tidal forces imparted on Mars by its moon Phobos.
This type of seismological study has never been performed on a planet other than Earth. The only other celestial body – until now – to receive this kind of scientific investigation has been the Moon.
In 1976, both of NASA’s Viking 1 and Viking 2 landers included seismometers mounted to the landers’ themselves, suffering from data corruption due to vibrations from the landers’ operation and the Martian wind jostling the two stations.
Despite these complications, one possible candidate for a marsquake was recorded by Viking 2 but could not be confirmed due to limitations of the seismometer and vibrations coming from the lander at the time of the quake indication.
Nonetheless, the Viking 1 and 2 seismometers confirmed no widespread or large marsquakes during the landers’ operational periods from 20 July 1976 to 13 November 1982.
Learning from the efforts of the Viking 1 & 2 seismometers, SEIS was designed to perform its Martian seismography while in physical contact with the Martian surface and off the lander.
SEIS consists of two primary components currently attached to the top of InSight that will have to be carefully placed one on top of the other by InSight’s Instrument Deployment Arm.
The first and most crucial element is the seismometer itself, SEIS: a tripod mounted, broad-band seismometer enclosed within a thermal vacuum case.
To provide as clear a possible picture of the seismic data, the instrument carries a host of meteorological tools to help better understand atmospheric events that could affect its seismic measurements.
These meteorological instruments include air temperature and wind direction and speed sensors from the Spanish/Finnish Rover Environmental Monitoring Station, a barometer from JPL, and a vector magnetometer to measure magnetic disturbances in Mars’ ionosphere from the University of California Los Angeles.
While characterization of the local weather environment for validity of the seismic data is important, minimizing that weather’s interference is also paramount. To that end, SEIS will be covered with a Wind and Thermal Shield (WTS) which will be placed over top of the experiment by the Instrument Deployment Arm after SEIS is safely on the Martian surface.
The WTS was designed, along with the Instrument Deployment Arm’s movement sensitivity, to fit snugly over top of SEIS – with just 6 centimeters (2.3 inches) between the outer wall of the seismometer and the inner edge of the WTS.
Deployment of SEIS will not come until teams back on Earth have reviewed all of the detailed images InSight’s cameras will return of the available deployment area – which is limited by the Instrument Deployment Arm’s range of motion.
SEIS, along with the other deployable science instrument, must be placed within the same 3 m long by 2 m wide crescent in front of InSight. Before deployment can happen, scientists must examine the entire crescent-shaped deployment zone, searching for any rocks and hazards that need to be avoided.
Once a complete understanding of the deployment zone is known, a specific location for SEIS’s placement will be chosen and the entire deployment process will be practiced on Earth before InSight’s arm is commanded to actually deploy the experiment.
Once SEIS is safely on the Martian surface, there will be a gap of about one week before its Wind and Thermal Shield is placed on top of it to allow for preliminary activation and calibration of SEIS.
This calibration includes taking preliminary measurements while the Instrument Deployment Srm is still grappled to the experiment so that SEIS can easily be moved should those initial calibrations prove unfavorable for the experiment’s overall goals.
All of these checkout activities are expected to happen within the first Martian day of deployment. If everything is satisfactory, the Instrument Deployment Arm will release SEIS for final experiment configuration before the arm places the Wind and Thermal Shield overtop of the seismometer.
SEIS has a targeted placement date on the Martian surface between 3-4 weeks after landing – which places its deployment in the mid- to late- December 2018 timeframe.
SEIS itself was primarily provided by the French Space Agency (CNES) in partnership with the Swiss Federal Institute of Technology, Imperial College, the Max Planck Institute for Solar System Research, the Institut de Physique du Globe de Paris, the Institut supérieur de l’aéronautique et de l’espace, and NASA’s Jet Propulsion Laboratory.
Heat Flow and Physical Properties Package:
The other deployable experiment for InSight is the Heat Flow and Physical Properties Package, HP3 – which carries primary mission objectives to understand the origin and diversity of the terrestrial inner planets of the solar system, determine weather Earth and Mars formed from the same material, and understand how active the interior of Mars is at present.
Built by the German Aerospace Center, with cooperation from the European Space Agency, and the Space Research Centre of the Polish Academy of Sciences, HP3 is a revolutionary planetary exploration tool that traces its origins to the failed 2003 Beagle 2 Mars lander mission.
HP3 was also unsuccessfully proposed for missions to Mercury, Mars, and the Moon before it was formally accepted in 2011 by NASA to be included as a payload aboard InSight.
Once placed on the surface, HP3 will self-penetrate as deep as 5 m (16 ft) below the Martian surface while leaving a trail of tethered heat sensors behind to measure the amount of heat streaming from the Martian core – which will in turn provide an understanding of how much heat is flowing out of Mars and what the source of that heat is (i.e., what Mars’ internal composition is).
“We know that Mars’ interior is not as warm as Earth’s, but we’ve never taken the planet’s temperature,” said Tilman Spohn, Principal Investigator for HP3. “HP3 will take Mars’ temperature, tell us how much heat is leaving the planet, and whether Earth and Mars formed from the same stuff.
“That’s key to learning not only about Mars, but about how all the rocky planets of the solar system formed and evolved.”
To answer these questions, HP3 must burrow itself deeper into Mars than any scoop or laser has gone before. And it has to do this autonomously given the distance between Earth and Mars.
Enter the self-hammering nail, nicknamed “the mole.” With the mole, HP3 will use a metal cylinder – called the HP3 penetrator – inside of which is a motor and roller system that will gradually rotate upwards, pulling a hammer up against a spring to increase tension.
The gearbox/motor will drive the roller counterclockwise and upwards around a roller axis. The roller has a small protrusion on one side to prevent the accidental release of the hammer.
After each full rotation, the roller protrusion will align perfectly with a groove, allowing the hammer, tensioned by the spring, to jolt downward and strike the tip of the mole – burrowing it deeper under the Martian surface with each strike.
As the mole moves further underneath the surface, it will pull a trail of sensors behind it that will take precise temperature readings every 10 cm (3.9 in).
More so, every 50 cm (1.5 ft) during the descent, the mole will emit a pulse of heat and monitor how that heat pulse interacts with the Martian crust. A quick degradation of the heat pulse would indicate a thermal conductor, metal, composition of the crust.
Rotation and Interior Structure Experiment:
The Rotation and Interior Structure Experiment, or RISE, is a NASA JPL radio science instrument that will use X band radio tracking with Earth to provide better understanding of Mars’ interior structure and composition.
It will be the first of the three major scientific instruments activated and, according to NASA’s InSight mission website, should already be functioning.
By using X band radio tracking, scientists on Earth will be able to precisely measure InSight’s location on the Martian surface to an accuracy of less than 2 cm (less than one inch).
Because scientists know exactly where InSight touched down, any change to its location observed through X band communications indicates a wobble, or nutation, in Mars’ axis of rotation.
With InSight’s X band systems, scientists will be able to monitor perturbations in Mars’ axial rotation to within 10 cm (7 inches).
By measuring that nutation over a period of time, a nutation amplitude can be determined. From there, the nutation amplitude, procession, and spin axis direction can be used to make more precise calculations of the size and density – and therefore the composition – of the Martian interior.
RISE will allow us to better understand if Mars’ core is mostly liquid – as planets with molten cores wobble more during their daily axial turns than do planets with solid cores – and which elements aside from iron are present in Mars’ core and mantle.
This type of information could also lead to a better understanding of why Mars has such a weak magnetic field compared to Earth.
A strong magnetic field like Earth’s helps shield a planet from the Sun’s solar winds which can strip away the upper portions of a planet’s atmosphere. Weaker magnetic fields like Mars’ provide for a greater rate of atmospheric escape, something which NASA’s MAVEN mission is currently studying from Martian orbit.
Moreover, RISE will also be able to determine Mars’ axial rotation changes due to hemispheric seasonal redistribution of carbon dioxide ice as it sublimates in summer and condenses at the poles in winter.
In addition to the three primary scientific investigations, InSight also contains two other experiments: Temperature and Winds for InSight (TWINS) and the Laser RetroReflector for InSight (LaRRI).
The TWINS experiment was provided by Spain’s Centro de Astrobiolagía and will serve as the main weather station and platform for InSight.
Sticking with European roots, LaRRI, provided by the Italian Space Agency, is a corner cube retroreflector that will enable passive laser range finding by the fleet of Martian orbiters.
LaRRI does not require any power or input from InSight, and thus will enable passing spacecraft to identify their distance from InSight and any changes to Mars surface height at InSight’s location long after the mission ends.