THE WOODLANDS, TEXAS — The darkish dunes of Titan, Saturn’s largest moon, might have fallen from area.
Greater than sufficient cometary materials might have struck Titan to have fashioned its huge dune fields, planetary scientist William Bottke reported March 12 on the Lunar and Planetary Science Convention. Pc simulations recommend that the enigmatic drifts fashioned from objects hailing from the primordial Kuiper Belt, a contemporary supply of comets past the orbit of Neptune. The proposed situation might additionally clarify the presence of comparable materials noticed on different worlds, mentioned Bottke, of the Southwest Analysis Institute in Boulder, Colo.
The character 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 huge as the large dunes discovered within the United Arab Emirates, says planetary geologist Jani Radebaugh of Brigham Younger College in Provo, Utah. These earthbound mounds are additionally the place the latest Dune movies had been shot (SN: 3/1/24).
The favored speculation contends that Titan’s undulating sands include natural particles produced by photo voltaic irradiation of its hazy ambiance (SN: 2/1/19). After these micron-sized particles fall to the floor, they one way or the other develop bigger into sand-sized grains that may kind dunes. But it surely’s not clear how precisely that development happens. What’s extra, laboratory exams present that the natural particles might break aside too simply to endure being buffeted into dunes, Bottke mentioned.
He and his colleagues suggest one other situation, one which begins early within the historical past of the photo voltaic system, roughly 4 billion years in the past.
Probably the most common theories for the photo voltaic system’s evolution says that the large planets migrated from the place they fashioned to their present positions (SN: 10/20/23). Throughout 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. However many comets would have additionally smashed collectively, pulverizing them into tiny particles.
We all know a shocking quantity about these particles, Bottke mentioned, as a result of many have struck spacecraft and Earth. They’re resilient sufficient to outlive passing by way of our ambiance. And so they’re darkish and sometimes round 200 microns large, simply the precise measurement to construct darkish dunes on Titan.
Bottke and his colleagues ran pc simulations on how Saturn, Jupiter and their moons advanced throughout this chaotic interval, monitoring how a lot pulverized comet mud and what number of massive impactors fell on Titan and different moons of Saturn and Jupiter.
Each the mud and the impactors might have delivered greater than sufficient materials to account for Titan’s dunes, the workforce discovered. “We now have two sources that may probably do that,” Bottke mentioned.
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 identified to have massive patches of darkish materials.
The darkish materials on Iapetus is believed to have hailed from elsewhere, notes Radebaugh, who was not concerned within the analysis. So it’s believable that Titan’s sands might 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. “Should you’re resurfacing by way of volcanism, that might 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, might resolve the thriller (SN: 6/27/19). “It’s a testable speculation,” says Melissa Coach, a planetary scientist at NASA’s Goddard House Flight Heart in Greenbelt, Md., who works on the mission. Devices onboard the rotorcraft will be capable of take measurements of the compositions of the dune particles, she says.
And so someday, maybe, a flying machine will verify that seas of shattered comets ripple on a distant moon.
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