Martian days are growing shorter, but we don’t know why

By Joshua Hawkins
Published Aug 13th, 2023 

Image: NASA/JPL-Caltech

New data gathered from NASA’s Insight Lander has revealed that Martian days are getting shorter every year. While the length of days is only getting shorter by a series of milliseconds, those small changes mean the planet is rotating faster and faster each year, and researchers aren’t sure exactly why.

InSight was retired last December and captured a good deal of data about the Red Planet during its operations. Looking through that data, NASA has discovered some intriguing information – Mars rotations are growing faster, accelerating by around four milliarcseconds per year.

While that isn’t a huge change, any rotation speed change in a planet could be serious, especially as those changes can add up over hundreds and even thousands of years. Right now, Martian days have a length of 24 hours and 37 minutes. These days are often referred to as “sols” and are used when describing how long spacecraft have been orbiting or watching the planet.

Image source: NASA/JPL-Caltech

Learning that the speed at which sols pass on Mars is increasing has left scientists baffled, because they just aren’t sure what’s causing the increase. As for the data itself, being able to look back at everything InSight learned before its retirement is great, as we can always learn more about the details that might not have stood out at the time, especially as we capture more data about Mars with Curiosity and Perseverance – two rover-based missions still exploring the Red Planet.

NASA has a plan to send a manned mission to Mars in the 2030s, though that does rely on some other factors to make it possible – including the creation of a nuclear-powered rocket engine. However, learning exactly why the length of days is growing shorter on Mars could be important to understanding more about the planet’s history, as well as its future.

A paper with full details is available in the journal Nature.