Are Titan’s dunes made of comet dust?

A brand new concept means that Titan’s majestic dune fields might have come from outer space. Researchers had all the time assumed that the sand making up Titan’s dunes was domestically made, via erosion or condensed from atmospheric hydrocarbons. However researchers from the College of Colorado need to know: May it have come from comets?

When the Cassini spacecraft arrived in orbit round Saturn, no one had ever seen beneath the thick soupy ambiance of Titan. So when it dropped the Huygens lander, and commenced probing Titan with cloud-penetrating radar, scientists had been stunned to be taught that Titan has a really Earth-like look.

It has a thick nitrogen ambiance, rain, rivers, oceans and large dune fields. However not like the dunes of Earth’s sandy deserts in Namibia and southern Arabia, Titan’s dunes are huge, and fill huge fields masking greater than an eighth of the enormous moon’s floor. These dunes are about 100 meters tall, 1 to 2 km vast on the base, and may stretch for a whole lot of kilometers in size.

Dunes on Earth are comprised of sand, which is blown by the wind and heaped into drifts. Particular person sand particles are nudged and blown by the wind with sufficient pressure to make them bounce and scatter in a course of known as saltation. If the particles do not bounce, then they can not pile up on prime of one another, but when the wind is ready to elevate them off the bottom utterly then they merely blow away. Saltation relies on the scale and mass of the sand particles and the power of the wind, but additionally wants the particles to be dry in order that they’ll transfer freely with out sticking collectively.

Titan’s geology

Titan is the second largest moon in your complete solar system, crushed solely by Ganymede, orbiting Jupiter. It’s Saturn’s largest moon, and really previous. Not like most of Saturn’s moons, which had been captured over time, Titan would have fashioned along with Saturn billions of years in the past.

Regardless of having so many options in widespread with Earth, it’s a very completely different place. It’s so intensely chilly that, as an alternative of water, its rain and rivers are comprised of liquid hydrocarbons like methane. Water, then again, is frozen into arduous ice; rocks on Titan are comprised of water ice, as an alternative of granite and basalt, and Titan’s equal of lava and magma are comprised of liquid water and ammonia.

Because of this sand on Titan shouldn’t be comprised of silica eroded from bigger rocks, since these supplies aren’t discovered on the floor. One fashionable concept is that it might as an alternative be comprised of ice. When liquid methane rains and flows, it might erode the water-ice bedrock, grinding chunks collectively to a sand of ice grains.

Another concept is that the sand particles are as an alternative comprised of tholins. These are discovered everywhere in the colder areas of the solar system, the place chilly hydrocarbons in comets or the outer atmospheres of planets and moons react with ultraviolet gentle from the sun to create advanced compounds. Tholins fashioned within the dry ambiance of Titan might clump along with static electrical energy to kind small grains of soot that then settle to the bottom, creating each dust and sand.

What do comets should do with this?

A paper introduced at this 12 months’s Lunar and Planetary Science Convention (LPSC) suggests a brand new concept: What if the sand got here from comets? Comets, as we all know, are comprised of supplies left over from the creation of the solar system. A lot of the primordial fuel and dust that collapsed from an historic nebula to kind the solar system would have ended up within the sun, with the majority of the stays forming the planets. However this is able to nonetheless have left a whole lot of materials floating free, and a few of that might have steadily coalesced into lumps of dust and ice, which we see as we speak as comets.

When comets are nudged into elliptical orbits and move via the inside solar system, a few of their ice heats up and sublimates into fuel which blows out, carrying dust with it. This dust is scattered all through the solar system, concentrated alongside the assorted comet‘s orbits. Particular person grains typically collide with the Earth, which we see as meteors, burning excessive in our ambiance. Current surveys in Antarctic ice fields, the place there is no such thing as a floor sand, have discovered many such particles which have survived atmospheric reentry.

However Earth shouldn’t be the one place the place these grains can find yourself. In response to the researchers, there was a time when an awesome many comets had been passing shut by Saturn and its moons. They ran simulations to review the evolution of the Kuiper Belt, utilizing a model of the Good mannequin. The Good mannequin, named for the town through which it was first introduced, says that the solar system was initially organized very otherwise from how it’s as we speak. Over time, the planets migrated to their present places.

Throughout this era, Neptune handed via the Kuiper belt, nudging many comets into new orbits. Many of those comets handed shut by Saturn and its moons, and a few even collided with the moons. The researchers counsel that a lot of the sand making up Titan’s dunes could also be particles from all these comets.

However is it true? This concept does match with what we presently know, and is supported by laptop modeling, however so do the opposite theories. Luckily, NASA lately confirmed that the Dragonfly mission might be launched in July 2028. Dragonfly is a lander, which might be despatched to Titan.

However not like earlier missions, this one is an 8-rotor flying drone. Just like the rovers on Mars, it will likely be capable of transfer to any areas of curiosity that scientists wish to examine additional. When it arrives in 2034, it should fly to dozens of places on Titan’s floor, and may settle the query as soon as and for all: Are the dunes of Titan actually constructed from comet dust?