Something Strange Happens on Mars During a Solar Eclipse

[Judi Lynn]

MICHELLE STARR
7 SEPTEMBER 2020



A transit of Phobos as seen by Curiosity in 2019. (NASA/JPL-Caltech/MSSS

The moons of Mars are not quite like our Earth's Moon. Phobos, the larger of the two, is much closer to its planet; compared to the Moon's 27-day orbit, Phobos swings around Mars in line with the planet's equator thrice every Martian day (sol).

Solar eclipses, therefore, are much more frequent than those here on Earth. Phobos passes in front of - but never entirely covers - the Sun for an annular or partial eclipse somewhere on Mars most sols. Because Phobos is moving so fast, it never transits for more than 30 seconds.

But, even during this brief time, the Mars InSight lander has recorded something peculiar happening.

To the surprise of Mars scientists, during Phobos eclipses, the lander's seismometer - the instrument that records ground motions to monitor possible quake activity - tilts, just an infinitesimal little bit, towards one side.

Researchers at ETH Zurich's Institute of Geophysics were actually studying data from Mars InSight to see if some of the effects of eclipses here on Earth also occur on Mars.

More:
https://www.sciencealert.com/something-strange-happens-on-mars-during-a-solar-eclipse

[gristy]

1. They figured it out

From the article:

This, the team believes, is the most likely cause of the strange reading.

"During an eclipse, the ground cools," said seismologist Martin van Driel of ETH Zurich. "It deforms unevenly, which tilts the instrument."

A similar effect was observed in 1997, at the Black Forest Observatory in Germany.

A technician forgot to turn off the light when leaving the seismometer vault, resulting in elevated noise in long-period data as the warmth from the bulb expanded the granite on which the seismometer rested.