Enlarge (credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstädt/Thomas Thomopoulos )

Ever since the Voyager mission sent home images of Jupiter's moon Io spewing material into space, we've gradually built up a clearer picture of Io's volcanic activity. It slowly became clear that Io, which is a bit smaller than Mercury, is the most volcanically active body in the Solar System, with all that activity driven by the gravitational strain caused by Jupiter and its three other giant moons. There is so much volcanism that its surface has been completely remodeled, with no signs of impact craters.

A few more details about its violence came to light this week, with new images being released of the moon's features, including an island in a lake of lava, taken by the Juno orbiter. At the same time, imaging done using an Earth-based telescope has provided some indications that this volcanism has been reshaping Io from almost the moment it formed.

Fiery, glassy lakes

The Juno orbiter's mission is primarily focused on studying Jupiter, including the dynamics of its storms and its internal composition. But many of its orbital passes have taken it right past Io, and this week, the Jet Propulsion Laboratory released some of the best images from these flybys. They include a shot of Loki Patera , a lake of lava that has an island within it. Also featured: the impossibly sheer slopes of Io's Steeple Mountain.

Enlarge (credit: Victor Leshyk)

The end-Triassic extinction, which happened 201 million years ago, was Earth’s third most severe extinction event since the dawn of animal life. Like today, CO ₂ rise and global warming were present, but the similarities don’t end there. As with today, it was a time of wildfires, deforestation, downpours, erosion, ocean acidification, marine dead zones, vanishing coral reefs, sea-level rise, and even insect plagues. There was also pollution by mercury, sulfur dioxide, halocarbons, and methane —and possibly even a damaged ozone layer.

“Something very violent occurred 201 million years ago, with great similarity in terms of CO ₂ with what we see is happening now,” said Dr. Manfredo Capriolo of the University of Oslo. That would seem to make it a good model to understand what’s going on now. But there are glaring differences—most notably the lack of humans.

Instead of the human pollution of today, the end-Triassic saw massive volcanic eruptions that emitted prodigious amounts of greenhouse gases and pollutants. There were other differences as well. During the Triassic, there was just one continent, called “Pangea,” and the climate started warmer and ice-free, with CO ₂ levels much higher than those of today. Dinosaurs had yet to dominate the planet, and there was no grass or flowers.

Enlarge / Scientists about to sink an Ocean Bottom Seismometer to the Atlantic seabed in 2021.

Scientists have scanned a section of the North Atlantic and revealed the remnants of what had been a huge pulse of hot rock that initiated a rapid climate warming event 56 million years ago.

The climate event, known as the Paleocene-Eocene Thermal Maximum (PETM), warmed the already-hot climate of the time by about 5.6° C due to a jump in atmospheric CO ₂ . Levels of that greenhouse gas rose from about 1,120 parts per million to about 2,020 ppm —much higher than today’s 417 ppm . Although it didn’t trigger a major extinction, it still exterminated some deep-sea creatures and tropical plants . Scientists want to understand the PETM better, because it’s an example of how the Earth reacted to a rapid rise in atmospheric CO ₂ a bit like we’re currently experiencing, albeit starting from a hot, ice-free climate.

Finding a cause

Although the cause of PETM has been debated since it was discovered in the 1990s , more and more evidence has accumulated that points to massive quantities of CO ₂ and methane emitted due to volcanic activity in the North Atlantic as the primary cause. This activity created what’s now known as the North Atlantic Igneous Province— the same kind of enormous volcanic phenomenon linked to climate disruption and extinctions at other times in Earth’s past, like the end-Triassic , the end-Permian , the early Jurassic , and others .

Enlarge / One of the rifts in the Cerebrus Fossae area, potentially created by the stretching of the crust driven by a mantle plume. (credit: NASA/JPL-Caltech/University of Arizona )

The Mars InSight lander included the first seismograph placed on the red planet, and it has picked up everything from marsquakes to impacts and provided lots of new information on Mars' interior. But perhaps its most striking finding has been that almost all of Mars' seismic activity appears to originate from a single location, a site called Elysium Planitia.

That area is also the site of the most recent volcanic activity we've detected on Mars. In a paper released this week, scientists argue that both derive from a single source: a plume of hot material rising through the mantle. It's the sort of geological activity that creates hotspots like Iceland and Yellowstone on Earth, but it had been thought that Mars had cooled too much to support those activities.

Building a case

Elysium Planitia is a generally flat region covering roughly a million square kilometers. It's just at the edge of Mars' northern lowlands, but it sits nearly a kilometer above them. Many of its features are old, including a series of ridges thought to be caused by the compression of Mars' interior as it cooled. But it also has signs of recent volcanic activity, though not nearly as much as the nearby Tharsis region, which contains Mars' largest volcanoes.