Vacuum Leak Discovered in Key Science Instrument for InSight Mission to Mars

Artist's conception of the InSight lander on Mars. Image Credit: NASA/JPL-Caltech
Artist’s conception of the InSight lander on Mars. The SEIS instrument is the dome-shaped object in the foreground. Image Credit: NASA/JPL-Caltech

One of the science instruments being installed on the InSight lander is experiencing a vacuum leak, according to an update posted Dec. 3 on the JPL website. The leak is in the vacuum container carrying the main sensors for the Seismic Experiment for Interior Structure (SEIS). The seismometer is one of the instruments which will be used to examine the subsurface of Mars at the landing site.

Three highly sensitive seismometers are enclosed within a sealed sphere. The leak was detected after the final sealing of the sphere. If not fixed, the leak would make it difficult for the lander to meet its science requirements for the mission. It is critical for the vacuum container to work properly, since the seismometers need to operate in a vacuum; the seismometers are extremely sensitive to ground movements, as small as the width of an atom. The instrument was provided for the mission by the French Space Agency (CNES).

Work is progressing on repairing the leak in time for a scheduled launch in March 2016. The instruments still need to be installed on the spacecraft and environmental tests conducted in France before launch.

The SEIS instrument package. Image Credit: Max Planck Institute for Solar System Research
The SEIS instrument package. Image Credit: Max Planck Institute for Solar System Research (MPS)

The lander itself has already completed construction and testing at Lockheed Martin Space Systems in Colorado. It is now being prepared for shipment to the launch site at Vandenberg AFB. The rest of the payload, including the Heat Flow and Physical Properties Package (HP3) from Germany, has already been installed on the spacecraft.

At this time, it seems that InSight is still on schedule for launch next March, and NASA and CNES managers are assessing the launch timeline.

While previous missions to Mars have focused on studying the surface and atmosphere, InSight will “look” far below the surface to examine rocks from earlier in the planet’s evolution. InSight is similar in design to the previous Mars Phoenix Lander, which landed near the Martian north pole in 2007. Re-use of the same technology helps to lower the risks and keep mission costs down.

InSight will be the first mission to Mars to permanently place instruments into the ground using a robotic arm. The two instruments include the seismometer and a heat-flow probe. The seismometer will measure tiny marsquakes which cause microscopic movements of the ground, which will help scientists better understand the interior of Mars. The heat-flow probe measures heat coming from the planet’s interior and will hammer itself about 3 to 5 meters (16 feet) deep into the ground. Even the radio can be used to measure wobbles in the planet’s rotation and environmental instruments to monitor weather and changes in the magnetic field. And, of course, there will be cameras—two of them.

The instruments on InSight include:

  • Grapple – Mechanism at the end of the IDA that grips the instruments during deployment
  • Heat Flow Probe – Hammering mechanism that pulls the temperature sensors down into the regolith
  • HP3 – Heat Flow and Physical Properties Package, the heat flow experiment
  • IDC – Instrument Deployment Camera, pointable medium-resolution camera
  • IDA – Instrument Deployment Arm
  • ICC – Instrument Context Camera, fixed wide-angle camera
  • Pressure Inlet – Wind-shielded opening for pressure sensor
  • RISE Antenna – X-band radio antenna for the Rotation and Interior Structure Experiment
  • SEIS – Seismic Experiment for Interior Structure, the seismometer
  • Tethers – Cables carrying electrical power, commands and data between the lander and instruments
  • TWINS – Temperature and Winds for InSight, environmental sensors
  • UHF Antenna – Antenna used for communication with orbital relay spacecraft
  • WTS – Wind and Thermal Shield protecting the seismometer from the environment

An animation of the InSight lander deploying its instruments can be seen below:

The overall main objective of InSight is to study how rocky planets like Mars and Earth formed. From the mission website:

“InSight’s primary objective will be to uncover how a rocky body forms and evolves to become a planet. Generally, a rocky body begins its formation through a process called accretion. As the body increases in size, its interior heats up and melts. As it subsequently cools and recrystallizes it evolves into what we know today as a terrestrial planet, containing a core, mantle and crust. While all of the terrestrial planets share similar structures and their bulk compositions are roughly the same as the meteoritic material from which they were formed, they are by no means uniform. Each of the terrestrial planets reached their current formation and structure through a process known as differentiation, which is poorly understood. InSight’s goal will be to solve the mystery of differentiation in planetary formation – and to bridge the gap of understanding that lies between accretion, and the final formation of a terrestrial planet’s core, mantle, and crust.”

Specific goals of the mission include:

The InSight mission will help scientists better understand the interior structure of Mars. Image Credit: NASA/JPL-Caltech
The InSight mission will help scientists better understand the interior structure of Mars. Image Credit: NASA/JPL-Caltech
  • Determine the size, composition, physical state (liquid/solid) of the Martian core
  • Determine the thickness and structure of the Martian crust
  • Determine the composition and structure of the Martian mantle
  • Determine the thermal state of Mars’ interior
  • Measure the magnitude, rate and geographical distribution of Mars’ internal seismic activity
  • Measure the rate of meteorite impacts on the surface of Mars

InSight is scheduled to land on Mars on Sept. 28, 2016.

Elsewhere on Mars, the Curiosity rover has been busy examining some sand drifts which are part of the larger Bagnold Dunes. These dunes stretch for miles along the base of Mount Sharp, and their dark color stands out starkly against the lighter terrain around them. These dunes are “active” in that they are gradually drifting across the surface, just like similar sand dunes on Earth. Previously, Curiosity had also seen ancient petrified dunes which have become hardened rock over time. Even though the Martian atmosphere is much thinner than Earth’s, wind can still create massive dunes and smaller drifts, just like in earthly deserts.

“We’ve planned investigations that will not only tell us about modern dune activity on Mars but will also help us interpret the composition of sandstone layers made from dunes that turned into rock long ago,” said Bethany Ehlmann of the California Institute of Technology and NASA’s Jet Propulsion Laboratory, both in Pasadena, Calif.

According to Nathan Bridges of the Johns Hopkins University’s Applied Physics Laboratory, Laurel, Md., “These dunes have a different texture from dunes on Earth. The ripples on them are much larger than ripples on top of dunes on Earth, and we don’t know why. We have models based on the lower air pressure. It takes a higher wind speed to get a particle moving. But now we’ll have the first opportunity to make detailed observations.”

As well as the dunes survey, analysis of the Big Sky and Greenhorn rock-powder samples by CheMin and SAM onboard the rover will continue over the next few weeks. These should provide even more clues as to the history of water in Gale crater, which Curiosity has already confirmed used to be a lake or series of lakes.

The Opportunity rover, meanwhile, is now entering its seventh Martian winter. Unlike previous years, however, the rover is expected to remain active instead of hibernating. The rover uses the tilt of a Sun-facing slope to keep its solar panels pointed toward the Sun and maintain power.

“Our expectation is that Opportunity will be able to remain mobile through the winter,” said Mars Exploration Rover Project Manager John Callas of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The shortest daylight period of this winter will come in January 2016. Opportunity has finished a “walkabout” survey of its current location in Marathon Valley, which is on the rim of the huge Endeavour crater. The rover is now zeroing in on rock outcrops which contain clay minerals, as identified previously from orbit, which will provide more information about past water activity in this region.

Intricately sculpted sand drifts on top of Dune 2, which is part of the Bagnold Dunes complex, seen by Curiosity. Image Credit: NASA/JPL-Caltech/Stuart Atkinson
Intricately sculpted sand drifts on top of Dune 2, which is part of the Bagnold Dunes complex, seen by Curiosity. The foothills of Mount Sharp are behind them. Image Credit: NASA/JPL-Caltech/Stuart Atkinson
View of Marathon Valley, taken by the Opportunity rover on Aug. 2, 2015. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.
View of Marathon Valley, taken by the Opportunity rover on Aug. 2, 2015. Image Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

“We have detective work to do in Marathon Valley for many months ahead,” said Opportunity Deputy Principal Investigator Ray Arvidson, of Washington University in St. Louis. “During the Martian late fall and winter seasons Opportunity will conduct its measurements and traverses on the southern side of the valley. When spring arrives the rover will return to the valley floor for detailed measurements of outcrops that may host the clay minerals.”

As Steve Squyres, principal investigator for the Opportunity mission at the Cornell University in New York, told The Planetary Society: “It’s great to be in Marathon Valley. It was a long haul. Based on the orbital data, the highest concentration of phyllosilicates we’ve ever seen with either rover is here. Just in terms of what we know about the place from orbit, it’s expected to be scientifically very productive.”

InSight may not be a rover, but it will greatly help scientists to understand what is happening below Mars’ surface, and how the planet evolved to be what it is today. That information, combined with the data from rovers and orbiters, is needed to fill in missing puzzle pieces as to how Mars formed and then changed from a warmer, wetter world to a cold and mostly dry one.

More information about the InSight mission is available here.


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