THE WOODLANDS, TEXAS — The darkish dunes of Titan, Saturn’s largest moon, may have fallen from area.
More than sufficient cometary materials could have struck Titan to have shaped its huge dune fields, planetary scientist William Bottke reported March 12 on the Lunar and Planetary Science Conference. Computer simulations counsel that the enigmatic drifts shaped from objects hailing from the primordial Kuiper Belt, a contemporary supply of comets past the orbit of Neptune. The proposed state of affairs may additionally clarify the presence of comparable materials noticed on different worlds, stated Bottke, of the Southwest Research Institute in Boulder, Colo.
The nature of Titan’s sand has lengthy been contemplated. Beneath the moon’s tangerine skies drift some 10 million sq. kilometers of dusky dunes (SN: 5/23/06). These waves of sand are about as large as the huge dunes discovered within the United Arab Emirates, says planetary geologist Jani Radebaugh of Brigham Young University in Provo, Utah. Those earthbound mounds are additionally the place the latest Dune movies had been shot (SN: 3/1/24).
The fashionable speculation contends that Titan’s undulating sands encompass natural particles produced by photo voltaic irradiation of its hazy environment (SN: 2/1/19). After these micron-sized particles fall to the floor, they someway develop bigger into sand-sized grains that may type dunes. But it’s not clear how precisely that development happens. What’s extra, laboratory exams present that the natural particles could break aside too simply to endure being buffeted into dunes, Bottke stated.
He and his colleagues suggest one other state of affairs, one which begins early within the historical past of the photo voltaic system, roughly 4 billion years in the past.
One of the most well-liked theories for the photo voltaic system’s evolution says that the large planets migrated from the place they shaped to their present positions (SN: 10/20/23). During this time, these planets are thought to have handed by way of the Kuiper Belt. That grand reshuffling would have led to the bombardment of Titan and different moons by comets. But many comets would have additionally smashed collectively, pulverizing them into tiny particles.
We know a stunning quantity about these particles, Bottke stated, as a result of many have struck spacecraft and Earth. They’re resilient sufficient to outlive passing by way of our environment. And they’re darkish and infrequently round 200 microns extensive, simply the correct measurement to construct darkish dunes on Titan.
Bottke and his colleagues ran laptop simulations on how Saturn, Jupiter and their moons advanced throughout this chaotic interval, monitoring how a lot pulverized comet mud and what number of giant impactors fell on Titan and different moons of Saturn and Jupiter.
Both the mud and the impactors may have delivered greater than sufficient materials to account for Titan’s dunes, the staff discovered. “We have two sources that may probably do that,” Bottke stated.
What’s extra, the simulations confirmed that a lot of the fabric additionally struck Jupiter’s moons Callisto and Ganymede and the Saturnian moon Iapetus, all of that are recognized to have giant patches of darkish materials.
The darkish materials on Iapetus is assumed to have hailed from elsewhere, notes Radebaugh, who was not concerned within the analysis. So it’s believable that Titan’s sands may have otherworldly origins too, she says.
Nonetheless, it’s unclear whether or not the fabric would stay on Titan’s floor after falling. Ice volcanoes could also be erupting, or have erupted, on Titan, Radebaugh says. “If you’re resurfacing by way of volcanism, that will create an issue for this [story].” Eruptions would subsume and bury the previous, fallen particles over time.
NASA’s Dragonfly mission to Titan, slated for launch in 2028, may clear up the thriller (SN: 6/27/19). “It’s a testable speculation,” says Melissa Trainer, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., who works on the mission. Instruments onboard the rotorcraft will be capable to take measurements of the compositions of the dune particles, she says.
And so sooner or later, maybe, a flying machine will affirm that seas of shattered comets ripple on a distant moon.
