NASA/JPL published this original article on December 20, 2024. Edits by EarthSky.
While we’re celebrating New Year’s Eve here on Earth, Mars scientists are ahead of the game: The red planet completed a trip around the sun on November 12, 2024, prompting a few researchers to raise a toast.
But the Martian year, which is 687 Earth days, ends in a very different way in the planet’s northern hemisphere than it does in Earth’s northern hemisphere. While winter’s kicking in here, spring is starting there. That means temperatures are rising and ice is thinning, leading to frost avalanches crashing down cliffsides, carbon dioxide gas exploding from the ground and powerful winds helping reshape the north pole.
Serina Diniega, who studies planetary surfaces at NASA’s Jet Propulsion Laboratory in Southern California, said:
Springtime on Earth has lots of trickling as water ice gradually melts. But on Mars, everything happens with a bang.
Mars’ wispy atmosphere doesn’t allow liquids to pool on the surface as on Earth. Instead of melting, ice sublimates, turning directly into a gas. The sudden transition in spring means a lot of violent changes as both water ice and carbon dioxide ice – dry ice, which is much more plentiful on Mars than frozen water – weaken and break.
Diniega said:
You get lots of cracks and explosions instead of melting. I imagine it gets really noisy.
Using the cameras and other sensors aboard NASA’s Mars Reconnaissance Orbiter (MRO), which launched in 2005, scientists study all this activity to improve their understanding of the forces shaping the dynamic Martian surface. Here’s some of what they track.
In 2015, MRO’s High-Resolution Imaging Science Experiment (HiRISE) camera captured a 66-foot-wide (20-meter-wide) chunk of carbon dioxide frost in freefall. Chance observations like this are reminders of just how different Mars is from Earth, Diniega said, especially in springtime, when these surface changes are most noticeable.
Diniega said:
We’re lucky we’ve had a spacecraft like MRO observing Mars for as long as it has. Watching for almost 20 years has let us catch dramatic moments like these avalanches.
Diniega has relied on HiRISE to study another quirk of Martian springtime: gas geysers that blast out of the surface, throwing out dark fans of sand and dust. These explosive jets form due to energetic sublimation of carbon dioxide ice. As sunlight shines through the ice, its bottom layers turn to gas, building pressure until it bursts into the air, creating those dark fans of material.
But to see the best examples of the newest fans, researchers will have to wait until December 2025, when spring starts in the southern hemisphere. There, the fans are bigger and more clearly defined.
Another difference between ice-related action in the two hemispheres: Once all the ice around some northern geysers has sublimated in summer, what’s left behind in the dirt are scour marks that, from space, look like giant spider legs. Researchers recently re-created this process in a JPL lab.
For Isaac Smith of Toronto’s York University, one of the most fascinating subjects in springtime is the Texas-size ice cap at Mars’ north pole. Etched into the icy dome are swirling troughs, revealing traces of the red surface below. The effect is like a swirl of milk in a café latte.
Noting that some are as long as California, Smith said:
These things are enormous. You can find similar troughs in Antarctica but nothing at this scale.
Fast, warm wind has carved the spiral shapes over eons, and the troughs act as channels for springtime wind gusts that become more powerful as ice at the north pole starts to thaw. Just like the Santa Ana winds in Southern California or the Chinook winds in the Rocky Mountains, these gusts pick up speed and temperature as they ride down the troughs, in what’s called an adiabatic process.
The winds that carve the north pole’s troughs also reshape Mars’ sand dunes, causing sand to pile up on one side while removing sand from the other side. Over time, the process causes dunes to migrate, just as it does with dunes on Earth.
Last September, Smith coauthored a paper detailing how carbon dioxide frost settles on top of polar sand dunes during winter, freezing them in place. When the frost all thaws away in the spring, the dunes begin migrating again.
Each northern spring is a little different, with variations leading to ice sublimating faster or slower, controlling the pace of all these phenomena on the surface. And these strange phenomena are just part of the seasonal changes on Mars: the southern hemisphere has its own unique activity.
Bottom line: A new and explosive year began on Mars on November 14, 2024. NASA and its partners are tracking the season’s strange and unique features.
Read more: Mars is racing toward opposition in January 2025: Start watching now!
The post Mars starts a new year: avalanches, icy explosions and dunes first appeared on EarthSky.
