Lakes may bubble up into ‘magic islands’ on Saturn’s Titan
Champagne is supposed to be bubbly. So is a foaming bath. But a mixture designed to mimic the frigid lakes on an alien moon? That’s a little more surprising. Especially when those bubbles come out of nowhere and explode. But that’s what Kendra Farnsworth and her colleagues found during a set of experiments designed to help the team understand how compounds like those found on Titan interact. The accidental bubble discovery could help explain one of the mysteries spotted by NASA’s Cassini mission – ‘magic islands’, bright patches on radar images that suddenly disappeared.
“At the beginning, it wasn’t the main goal of the study, but it was one of those really surprising results,” Farnsworth, a doctoral student in planetary science at the University of Arkansas, said. “Bubbles had been predicted on Titan, but nobody had actually seen them or created them in a laboratory.”
In the experiment where the bubbles first appeared, Farnsworth had set out to measure how much nitrogen gas would dissolve in different mixtures of liquid methane and ethane, the organic compounds that make up Titan’s strangely Earthlike system of rainfall, lakes and seas. As she warmed up these ponds, Farnsworth noticed small bubbles would snake to the surface. But the real surprise came in a different experiment,
Farnsworth said, one based on slowly adding liquid ethane into liquid methane at Titan’s surface temperature.
Particularly interesting was the slightly warmer scenario meant to mimic modern Titan. In these experiments, the team found, two factors had to change simultaneously: the temperature of the liquid and the relative proportion of methane and ethane. The combination of changes takes the mixture from stillness to a spurt of bubbles. “There’s nothing and they explode,” Farnsworth said. “They’re more violent than we ever expected.”
For the first time, astronomers have gotten an up-close view of eruptions from an asteroid, shedding light on what might drive such explosions. The findings suggest that many asteroids may be similarly active and reveal that rocks blasting off asteroids may be a new way for meteorites to reach Earth, the scientists wrote in a new study.
Previous research found that a small number of asteroids could actively erupt with large amounts of dust and bits of rock. Much remains unknown about what drives such outbursts in active asteroids. Now, scientists have captured images of eruptions from the near-Earth asteroid Bennu. “This is the first view of an active asteroid this close up,” Harold Connolly, a sample scientist for the OSIRIS-REx mission, told space.com. Scientists chose to send OSIRIS-REx to Bennu because the space rock looks similar to known active asteroids. But they hadn’t seen any eruptions from Bennu until now.
The researchers spotted three large eruptions from Bennu in January and February of this year, each ejecting a maximum of 200 chunks up to ten-centimetres (four-inches) across at top speeds of about 11.9 kilometres (7.4 miles) per hour. They also detected eight smaller eruptions that ejected about 20 or fewer bits of asteroid.
The scientists also discovered six chunks of rock around Bennu that they suggested were ejected during eruptions and stayed gravitationally bound to the asteroid. Some ultimately escaped into interplanetary space, and the others eventually fell back to Bennu’s surface.
These findings suggest that all carbonaceous asteroids may be active. Future research can look for more eruptions from Bennu, Connolly said. Scientists can also search the asteroids for craters that might have originated as sites of either eruptions or impacts of erupted material, he added.