May 20, 2019

What do you call an earthquake on Mars? A marsquake! For the first time, scientists working with the United States National Aeronautics and Space Administration (NASA) think they have detected an actual temblor on the red planet.

Scientists think they have detected marsquakes on Mars, the fourth planet from the sun. Credit: NASA/JPL/Malin Space Science Systems

At the end of 2018, NASA’s InSight probe deployed a specially-built seismometer called Seismic Experiment for Interior Structure (SEIS) to the surface of Mars. (InSight is short for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport. InSight launched from Earth in May 2018 and landed on Mars in late November.) On April 6, 2019, SEIS picked up faint vibrations that were not caused by wind or the movement of InSight’s robotic arm. The signal was faint, with a low-level magnitude between 1 and 2 on the Richter scale. On Earth, such a weak quake would go unnoticed. On Mars, however, InSight was there to feel it.

Mars is the third body on which humans have recorded seismic activity, after Earth and the moon. On Earth, quakes are caused by the bending and grinding of huge tectonic plates, which float on layers of soft rock and magma and hold the planet’s oceans and continents. Mars does not have tectonic plates. Marsquakes are likely caused by the shrinking of the planet’s interior, which itself is caused by the slow cooling of its core.

NASA’s InSight probe has been studying the surface of Mars since late November 2018. Credit: NASA/JPL-Caltech

While detecting marsquakes is exciting, readings from SEIS might also shed light on the structure of the red planet. Scientists have reason to think that Mars, like Earth, has an interior composed of a rocky outer crust, a soft mantle, a liquid outer core, and a solid inner core. But they do not know how thick each of the layers are. Seismic waves change direction slightly when passing through core layers. If scientists know the source of the seismic waves, they can get an idea of the kinds and sizes of layers the waves had to pass through to reach the seismometer. Scientists can then create a more accurate map of the Martian interior and gain insight into the structure of all rocky planets—including those in our solar system and those orbiting stars millions of light-years away.

InSight has many instruments in addition to SEIS. The probe also serves as the only weather station on another planet. Sensors track the brisk wind gusts, low pressures, and frigid temperatures of Elysium Planitia, a vast plain near the Martian equator. On May 11, the temperature climbed to -4 °F (-20 °C) during the day, but plummeted to -148 °F (-100 °C) during the Martian night. Wind speeds topped out at 32 miles (51 kilometers) per hour.

June 7, 2018

Last month, on May 5, the United States National Aeronautics and Space Administration (NASA) launched a new Mars probe called Insight from Vandenberg Air Force Base in California. InSight is short for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport. InSight, a probe that will study the formation of Mars, is NASA’s first interplanetary mission launched from the west coast of the United States. All previous such launches took place at Cape Canaveral Air Force Station in Florida.

This artist’s rendition shows the InSight lander operating on the surface of Mars. The probe is scheduled to land on Mars on Nov. 26, 2018. Credit: NASA/JPL-Caltech

The InSight mission cost just $814 million, a relatively small sum in the multibillion-dollar science of space exploration. The bargain probe will break new ground, however, quite literally, by drilling into the Martian surface. It will sample temperatures, measure the magnetic field, and record seismic levels, all to help scientists understand the planet’s formation. The data may also shed light on the formation of Earth and our solar system.

A NASA Atlas V rocket carrying InSight breaks through the clouds above Vandenberg Air Force Base in California on May 5, 2018. Credit: Cory Huston, NASA

Earth has three major layers: the crust, the mantle, and the core. Planetary scientists think our solar system’s other rocky planets—Mercury, Venus, and Mars—also have these layers. Scientists are unsure, however, how thick the layers are in the other planets. Earth has churned itself up through the process of plate tectonics, changing the chemical makeup and size of its layers over time. But Mars, the fourth planet from the sun, has experienced much less seismic activity. The planet’s present structure, then, should somewhat resemble its original composition when the solar system was formed.

Beginning in late November 2018, NASA’s InSight probe will study the formation of Mars, the fourth planet from the sun. Credit: NASA/JPL/Malin Space Science Systems

InSight carries three instruments vital to its mission. The Seismic Experiment Interior Structure (SEIS) sensor will study seismic waves from marsquakes (the Martian equivalent of earthquakes) to determine the structure of the interior of Mars. The Heat Flow and Physical Properties Package (HP³) will drill down almost 15 feet (5 meters) below the Martian surface—the deepest extraterrestrial excavation to date. As it drills, HP³ will record temperature changes to see how much heat remains from Mars’s formation billions of years ago. Scientists can determine the age of rocks, fossils, and other objects by measuring the radioactive elements in them, a science called radiogeology. A third InSight instrument will measure Mars’s magnetic field.

In an unusual arrangement, a robotic arm will move SEIS and HP³ from docks on the body of the lander to the surface of Mars. Tethers will control and power the instruments. Other than that, InSight’s design is pretty standard. Engineers reused much of the design of NASA’s Pheonix lander, which, in 2008, studied the history of water on Mars. By reusing this successful design, engineers saved many millions of dollars on the mission.

Two CubeSats (miniature satellites) hitched a ride on InSight’s rocket and are also traveling to Mars. The CubeSats are the first such satellites to venture beyond Earth’s orbit, and they will help transfer data from InSight during the probe’s landing.

InSight is scheduled to land on Mars on Nov. 26, 2018. Despite NASA’s strong recent record for Mars missions and the use of the proven Phoenix platform, success is far from guaranteed. Over the years, nearly two-thirds of all Mars missions have failed before completing their planned observations.