Listening for Impacts on Mars

In January 2019, NASA's InSight mission placed the first seismometer on the surface of Mars to record tiny ground movements—marsquakes—produced by faulting, meteorite impacts and other geological processes. During nearly four years of successful operation, more than a thousand marsquakes have been used to determine how tectonically active the surface of Mars is today and to reveal the internal structure of Mars. Marsquakes definitively generated by meteorite impacts, however, were conspicuously absent during the first almost one thousand Mars days of operation. In late 2021, however, InSight detected several seismic signals with an unusual fingerprint, suggestive of a exogenic source. Subsequent imaging by orbiting spacecraft revealed the smoking gun: an impact crater or cluster of craters several metres across in each case.

The first confirmed seismic detections of meteorite impacts on Mars help us to understand the seismic hazard of impacts and allows a re-evaluation of the origin of dozens of other marsquakes in InSight's catalog with characteristics similar to the confirmed impact-generated signals. Impact rates on Mars are not well understood and have traditionally been estimated by a combination of numerical modelling of the break-up of small meteoroids in Mars’ thin atmosphere and newly observed craters in recent orbital images of Mars' surface. In this talk, I will discuss how impact marsquakes detected by InSight provide a new and independent estimate of the current rate of small impacts on Mars. As small-crater counting is the principal means for dating small, young or active surfaces on Mars, an improved cratering rate is vital for establishing an accurate timing of recent geologic activity on Mars. It will also allow us to better correlate planetary surface ages across our Solar System.

Biography

Gareth Collins is a Professor of Planetary Science in the Department of Earth Science and Engineering, at Imperial College London. He received a BSc in Geophysics from the University of Liverpool (1998) and a PhD from Imperial College London (2002), before working as a post-doctoral researcher at the Lunar and Planetary Laboratory at the University of Arizona, USA. He returned to the UK and Imperial College in 2004 as a NERC post-doctoral Research Fellow and then Advanced Research Fellow, before being appointed as a permanent member of academic staff in 2011 and Professor in 2018. Gareth’s research explores the many consequences of impacts in the solar system through the development and application of numerical impact models. Major research contributions include studies of the formation of the Chicxulub impact crater and its role in the K-Pg mass extinction, as well as the formation of many other craters on Earth, the Moon and the role of collisions in the early solar system. He was a co-investigator on NASA’s InSight mission to Mars and on the Science Investigations Teams of NASA’s DART mission and ESA’s Hera mission. He was awarded the Barringer Medal of the Meteoritical Society in 2022 for contributions to impact cratering.