Comets might be the source of Titan's dark dunes

The dark dunes on Titan, Saturn's largest moon, might originate from space, stated planetary scientist William Bottke at the Lunar and Planetary Science Conference, who revealed on March 12 that an excess of cometary material could have hit Titan, leading to the creation of the enormous dune fields that riddle its surface. Bottke's computer simulations claimed these baffling drifts could be made up of objects that originate from the ancient Kuiper Belt, a contemporary comet source beyond Neptune's orbit. This notebook describes how a similar situation may explain the existence of similar material seen on other planets, he added.

Bottke, from the Southwest Research Institute in Boulder, Colorado, talked about the mystery of Titan's sand. Beneath the moon's orange skies, about 10 million square kilometers of murky dunes float around. These sandwaves, similar in size to the substantial dunes in the United Arab Emirates, have long been debated by scientists, stated planetary geologist Jani Radebaugh of Brigham Young University in Provo, Utah.

The standard theory claims that Titan's wavy sands are made up of organic particles, which are the result of solar radiation of its thick atmosphere. When these microscopic particles drop to the surface, they theoretically grow bigger into grains of sand that form into dunes. However, it hasn't yet been specified how this growth process happens. Additionally, lab trials have demonstrated that organic particles may be too frail to withstand the dune transformation process, mentioned Brottke.

Together with his colleagues, Bottke highlighted an alternative hypothesis, proposing that everything started about 4 billion years ago, at the dawn of our solar system.

One of the widely accepted theories about the solar system's formation infers that the migration of the gigantic planets from their origination points to their current positions, during which they must have traversed the Kuiper Belt. This large-scale upheaval could have caused a hailstorm of comets on Titan and other moons, leading to numerous comet collisions.

Bottke stated that ample data is available about these miniature particles, as they've hit numerous spacecraft and Earth, hence proving their resilience to atmospheric traversal. The particles' dark nature and roughly 200-micron size make them perfect for creating Titan's dark dunes.

Computational simulations were run by Bottke and his team on the evolution of Saturn, Jupiter, and their moons during this tumultuous era, tracking the quantity of destroyed comet dust that fell on Titan and some other moons of Saturn and Jupiter.

The team found that the comet dust and large impactors could have contributed enough material to justify Titan's dunes. Moreover, the simulations displayed that a fair amount of this material also hit Jupiter's moons Callisto and Ganymede and Saturn's moon Iapetus, with all satellites known for their large patches of dark material.

However, Radebaugh, who was not part of the research, revealed that the dark material on Iapetus is believed to have come from somewhere else, meaning the sands on Titan might share similar extraterrestrial origins.

Yet, it remains uncertain whether the materials would stay on Titan's surface upon landing. Titan may be experiencing, or might have undergone, ice volcanoes' eruptions, put forth Radebaugh, adding that volcanic activity would obscure and bury old, fallen debris over time.

However, with the expected 2028 launch of NASA's Dragonfly mission to Titan, this conundrum might be solved. Melissa Trainer, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, believes the onboard rotorcraft instruments could potentially take measurements of the dune particles' compositions. Trainer envisions a day when this mission can confirm that seas of fragmented comets indeed exist on a far-off satellite.