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.

December 2, 2013

Hundreds of earthquake tremors recorded by scientists in Antarctica have rocked the geological world by producing evidence of the first active volcano found so far inland on that frozen continent. Numerous volcanoes, both active and extinct, have been found along the Antarctic coastline and on nearby islands.

The earthquake swarms originated about 15 to 25 miles (25 to 40 kilometers) below the surface, near the Executive Committee Range in the Marie Byrd Land region of West Antarctica. The ice in that region is about 0.5-mile (0.8 kilometer) thick. The scientists, led by researchers from Washington University in St. Louis, stressed that they did not detect an actual eruption. Instead, the tremors likely resulted from the fracturing of rock as flowing magma and fluids opened new channels within the volcano. The tremors occurred beneath a 3,200-foot- (1,000-meter-) tall bulge under the ice that may be the cone (peak) of a volcano that formed sometime in the past as lava erupted from the volcano’s vent (opening).

The scientists detected the tremors while towing seismic equipment across the icy surface in 2010 and 2011 to map the structure of Earth’s mantle, the layer between inner core and outer crust. The seismic vibrations the scientists detected in Antarctica were nearly identical to so-called deep, long-period earthquakes (DLP’s) that have been detected beneath volcanoes in Alaska and Washington state. Although DLP’s sometime precede eruptions, scientists do not know if the tremors in Antarctica are signs that an eruption will occur there in the near future.

Volcanoes are common in Antarctica. Some are active, and others are hidden beneath the ice. But most of the known volcanoes are along the coastlines of the continent. © Rod Planck, Photo Researchers

If the volcano was to erupt, some of the ice above the vent would certainly melt, producing millions of gallons (liters) of water. Such a massive infusion of meltwater would speed of flow of nearby ice streams (slowly flowing “rivers” of ice within ice sheets). But unless the eruption was historically massive, it almost certainly would not melt all of the ice above. Scientists stressed that the greatest threat to Antarctica is still climate change. The Pine Island Glacier in West Antarctica, for example, is shrinking faster than any other glacier on Earth. It also ranks number one among glaciers whose melting is contributing to the rise of global sea levels.

Additional World Book articles:

• Science in Antarctica
• The Great Meldown