This artist's concept that depicts NASA's InSight Mars lander fully deployed for studying the deep interior of Mars.

Artist's Concept of InSight Lander on Mars: InSight was the first mission dedicated to investigating the deep interior of Mars. The findings will advance understanding of how all rocky planets, including Earth, formed and evolved.

Taking the Temperature on Mars

The Heat Flow and Physical Properties Package, HP3 for short, was designed to burrow down to almost 16 feet (5 meters) into Mars' surface. That's deeper than any previous arms, scoops, drills, or probes before it. Like studying the heat leaving a car engine, it sought to measure the heat coming from Mars' interior to reveal how much heat is flowing out of the body of the planet, and what the source of the heat is. This instrument was designed to help scientists determine whether Mars formed from the same stuff as Earth and the Moon, and gives them a sneak peek into how the planet evolved.

The HP3 was designed, built and managed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, or DLR), with significant contributions from the Space Research Center (CBK) of the Polish Academy of Sciences and Astronika.

Tech Specs

Main Job HP3 was designed to measure the heat flowing out of the interior of the planet, allowing us to infer Mars' temperature deep in the planet.
Location Mounted on the lander deck for the trip to Mars. After landing, the lander's arm picked up HP3 and placed it on the surface. The mole then began to hammer itself under the surface but encountered different soil properties than expected and was unable to reach the desired depth.
Mass Just over 6.5 pounds (about 3 kilograms), including the control electronics inside the lander.
Power A maximum of 2 watts while burrowing underneath the surface.
Volume About 5.3 gallons (20 liters) in total, including the control electronics inside the lander.
Data Return 350 megabits over the course of the mission.
"We’ve learned a lot that will benefit future missions that attempt to dig into the subsurface."
- Tilman Spohn, Principal Investigator

5 Things to Know

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    Designed to Take the Temperature
    HP3 was designed to take the temperature of the interior of Mars, much as a thermometer measures a person’s body temperature.
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    Trying Something New
    No mission before InSight had tried to burrow into the soil.
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    Unique Soil
    The mole’s design was based on soil seen by previous Mars missions – soil that proved very different from what the mole encountered. The spike-like probe design relied on friction with the surrounding material, but the soil’s unexpected tendency to clump together prevented it from reaching the desired depth.
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    A Helping Hand
    Using the lander’s robotic arm to assist, the team got the top of the mole about 2 or 3 centimeters under the surface. They used a scoop on the arm to scrape soil onto the probe and tamp it down to provide added friction, but the mole’s progress remained unchanged.
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    Informing Future Missions
    The team learned a lot about soil properties on Mars and how to creatively troubleshoot a challenging problem from millions of miles away–valuable lessons for future Mars explorers.

How It Worked

The mole was built to burrow down to almost 16 feet (5 meters) to remain unaffected by the changes in the seasons. As it descended, it pulled behind it a “tether” which, in addition to the electrical lines to power the mole, had temperature sensors embedded in it every 12 inches (30 centimeters). These allowed the probe to measure a tiny increase in temperature with depth. The mole was also designed to pause every 1.5 feet (50 centimeters) and put out a pulse of heat for its sensors to watch how the heat pulse decreases with time. If the crust material were a good conductor of heat, like metal, the pulse would decay quickly. If it is a poor conductor, like glass, the pulse would decay slowly. With these two measurements, scientists could estimate the temperature at much greater depths in the planet and how heat flows inside Mars.

How Heat Escapes Mars

Like studying the heat leaving a car engine, HP3 was designed to study the heat coming out of Mars, to shed light on what's producing the heat. This information could tell scientists whether Earth and Mars are made of the same stuff, and how heat flows inside Mars.

All planets have heat buried within them. Some, like Earth for example, are hotter than others, such as Mars. This heat comes from radioactive elements that were present in the material that first formed the planet, and energy left over from the process of planet formation. It gives rise to magnetic fields, mountains, and movement in the crust, which causes quakes. HP3 was designed to study the heat escaping from Mars to determine how fast the "engine" of the planet is running and what's fueling it.

Are Earth and Mars Siblings?

Scientists suspect that Mars was born from the same planet-forming material as Earth and the Moon. How Mars' fuel, its heat-producing radioactive elements, are distributed in the planet today is still an open question. The information from InSight's heat flow probe and its seismometer together were designed to help answer this question.