Emily Lakdawalla is Senior Editor and Planetary Evangelist at The Planetary Society. Her new book is The design and technique of curiosity: how the Mars Rover performs its task .
Even when hidden in a test lab in Colorado, the instrument takes thousands of people miles away. This is the kind of sensitive equipment that travels on Mars, where NASA's next mission will enter the mysterious history of the Red Planet and find out how active our neighbor world is.
Next On May 5, NASA will launch InSight, which is dedicated to the exploration of interiors with seismic surveys, geodesy, and heat transfer. Over the course of two Earth years, the lander will try to answer basic questions about the depths of Mars, including the thickness of its onion-like layers and how fast Mars will cool. It will bring new insights into the hidden history and mysterious presence of this planet.
The Long Journey
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When the Mars InSight mission launches on an Atlas V rocket from Vandenberg Air Force Base in California, it marks the United States' first interplanetary launch from the west Coast. NASA prefers to fire its largest missions from Florida, where they can zoom out beyond the ocean and use the Earth's eastern rotation to boost Earth's near-earth orbit. This strategy saves fuel that the mission will need later.
From the west coast it is uncertain to start to the east; Vandenberg usually starts south in orbits that go from one pole to another. It costs more fuel to reach Earth Orbit from Vandenberg than Florida, but the InSight's Atlas Centaur rocket combination is overwhelmed compared to its needs. Even after she has gone into a more expensive polar orbit, she will have enough fuel left to bring the relatively small spaceship on its interplanetary journey.
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InSight will launch a pair of CubeSats, the first of these tiny satellites to fly to another planet. MarCO, or Mars Cube One, consists of two identical spacecraft. If successful, they will broadcast real-time telemetry from InSight to Earth as the lander experiences its "seven minutes of terror" on November 26, 2018, from entering, descending, and landing on Mars.
To transmit over the 150 million kilometers That will separate Earth and Mars on the landing day. The MarCO satellites will use an innovative "Reflect Array" system. This is a flat X-band radio antenna that operates at a lower power than conventional antennas. If none of the MarCOs survives the journey to Mars, we will still receive "sounds" on Earth from the spaceship's low gain antenna to indicate the success of critical moments on its landing. The Mars Reconnaissance Orbiter, another mission that has been orbiting Mars since 2006, will record everything broadcast by InSight for later review if something goes wrong.
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This is not a brave little rover. InSight will not move through the Martian landscape like NASA's charismatic opportunity and curiosity bots. The landing site of the mission has been deliberately chosen to be as mild as possible in terms of both geology and weather. InSight will conduct his scientific experiments carefully and intentionally for about four months, and then it will sit there.
And sit down.
And sit down.
For two whole earth years.
One reason for the stationary nature of InSight is that the sophisticated tools must remain quiet and still. The heart of the mission is the Seismic Experiment for Inner Structure (SEIS), which can hear exquisitely sensitive seismometers, the oceanic noise of Colorado. After landing, InSight lifts SEIS off its deck and places the tool on a flat spot on the ground. Direct contact with the ground will dramatically increase SEIS's ability to detect minute ground motion and reduce temperature variations between day and night.
InSight will also cover SEIS to isolate it from temperature fluctuations and protect against wind. A range of environmental sensors provided by the same people doing the Curiosity weather experiments will help the SEIS remove noise in the data caused by weather, temperature and even magnetic field fluctuations.
SEIS will be able to discover Marsquakes. One of the basic questions it will answer is how much seismic activity is there on Mars. Mars has no plate tectonics like the Earth, so its seismicity is expected to be much more like that of the Moon: relatively small vibrations and creaking sounds caused by the very slow cooling and shrinking of the planet. It will also detect asteroid impacts or puffs of air, determining the current rate of impact on Mars. SEIS can even detect tiny signals from nearby Dust devils and the passing Mars moon Phobos.
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By measuring the arrival times of various types of seismic waves-including compression (P) waves traveling faster, and shear (S) waves traveling slower seismologists can find out the distance to seismic events. By studying the arrival times of other waves that have been reflected by discontinuities in the subsurface, such as the crust-mantle boundary, they can measure the crustal thickness, another of InSight's scientific goals.
In addition to SEIS, InSight includes a second instrument, the Heat Flow and Physical Properties Probe (HP 3 pronounced "H-P cubed"). HP 3 has a 40-inch "mole" that drills into the ground. Inside his cylinder is a spring-loaded tungsten block that will hammer thousands of times to propel the mole slowly to a depth of 3 meters or about 10 feet.
The mole will track a cable containing temperature sensors and heaters. The heating elements and sensors are used to measure how fast the Mars regolith conducts heat, and then the temperature sensors are used to measure the thermal gradient (how much and how fast the temperature changes with depth). Heat flux is a fundamental quantity that affects the physics of the interior of a planet. InSight's heat flux measurements will greatly enhance the geophysicists' understanding of Mars.
A final experiment will use the radio station to send a signal to earth-based antennas. Over the course of a Mars year, radio scientists will measure the position of InSight in the sky and use this information to measure the rotation of Mars. Why? The axis of rotation of Mars shifts very easily over time, in a way that is sensitive to the size of the core and how much of it has melted. As you study the rotation in detail, you will learn about its interior.
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InSight must remain calm and motionless for two years for his experiments to be successful, and so the mission can compile statistics and study changes throughout a Martian year. The three experiments are based on incredibly precise measurements of tiny ground movements and tiny temperature gradients.
While there may have been some exciting results from an early age, such as the discovery of an asteroid impact by its seismic waves, the real scientific payoff will not come until the experiment is completed and the scientific team has removed all the false contributions made by the Instruments measured signals. Then it's time to update the textbooks.