This article was originally published in The Conversation. (opens in a new tab) The post contributed to Space.com’s Expert Voices: Op-Ed & Insights article.
Andrew Gunn (opens in a new tab), Professor at Monash University
What is it like to be on the surface of Mars or Venus? Or even farther away, such as Pluto, or Titan, Saturn’s moon?
This curiosity has driven advances in space exploration since Sputnik 1 was launched 65 years ago (opens a new tab). But we are just beginning to scratch the surface of what is known about other planetary bodies in the solar system.
Our new study (opens in a new tab), published on May 19 in Nature Astronomy, shows how some unlikely candidates, namely sand dunes, can provide an insight into the climate and conditions you might face. experiment if you were in a distant planetary body.
Related: Strange “blue” dunes smear the surface of Mars in the NASA photo
What’s in a grain of sand?
The English poet William Blake wondered (opens in a new tab) what it means to “see a world in a grain of sand.”
In our research, we have taken it literally. The idea was to use the mere presence of sand dunes to understand the conditions on the surface of a world.
For the dunes to even exist, there are a couple of “Golden Rites (open a new tab)” criteria that must be met. The first is a supply of erodible but durable grains. There must also be winds fast enough to make these grains jump to the ground, but not fast enough to carry them into the atmosphere.
Until now, direct measurement of winds and sediments has only been possible on Earth and Mars. However, we have observed wind-driven sediment features in several other bodies (and even comets (opens in a new tab)) via satellite. The very presence of these dunes in these bodies implies that the conditions of Ric d’Or are met.
Satellites have captured images of wind features (from the top left, clockwise) of Earth, Mars, Titan, Venus, Pluto, and Triton. (Image credit: Nature Astronomy / Adapted Image by Gunn and Jerolmack (2022))
Our work focused on Venus, Earth, Mars, Titan, Triton (Neptune’s largest moon), and Pluto. Unresolved debates about these bodies have lasted for decades.
How can we square the apparent features blown by the wind on the surfaces of Triton and Pluto with their thin, faint atmospheres? Why do we see such a prolific activity of sand and dust on Mars, despite measuring winds that seem too weak to withstand it?
And does Venus’s thick, stiflingly hot atmosphere move the sand in a way similar to how air or water moves on Earth?
Extending the debate
Our study provides predictions of the winds needed to move sediments from these bodies and how easily this sediment would break in these winds.
We constructed these predictions by gathering the results of a number of other research papers and testing them with all the experimental data we could have in our hands.
We then applied the theories to each of the six bodies, based on measurements from telescopes and satellites of variables such as gravity, atmospheric composition, surface temperature, and sediment strength.
Studies prior to ours have analyzed the wind speed threshold required to move sand or the strength of various sediment particles. Our work combined them, looking at how easily the particles could break in the time they carry the sand in these bodies.
Wind ripples in the dunes of Bagnold on Mars were photographed by the Curiosity rover. (Image credit: NASA / JPL-Caltech / MSSS)
For example, we know that the equator of Titan has sand dunes, but we are not sure what sediment surrounds the equator. Is it pure organic mist (opens in a new tab) that rains from the atmosphere or mixes with denser ice?
As a result, we discovered that loose aggregates of organic fog would disintegrate into a collision if blown by the winds at Titan’s equator.
This implies that Titan dunes are probably not made of purely organic mist. To build a dune, sediments must be moved by the wind for a long time (some of the Earth’s dune sands are a million years old (it opens in a new tab)).
We also found that wind speeds would have to be too fast for Pluto to carry methane or nitrogen ice (which is what was supposed to be the sediments of Pluto’s dunes). This calls into question whether the “dunes” of Pluto’s plain, Sputnik Planitia (opens in a new tab), are dunes.
Instead, they can be sublimation waves (opens in a new tab). These are dune-like landforms made from the sublimation of material, rather than sediment erosion (such as those seen in the north polar cap of Mars).
Our results for Mars suggest that more dust is generated from wind-driven sand transport to Mars than to Earth. This suggests that our Martian atmosphere models may not effectively capture Mars’ strong “katabatic” winds, which are cold gusts that blow downhill at night.
Space exploration potential
This study reaches an interesting stage in space exploration.
For Mars, we have a relative abundance of observations; five space agencies are conducting active missions in orbit or in situ. Studies like ours help inform the goals of these missions and the paths followed by rovers such as Perseverance (opens in a new tab) and Zhurong (opens in a new tab).
At the outer limits of the solar system, Triton has not been observed in detail since the flyby of NASA’s Voyager 2 in 1989. There is currently a mission proposal (opens in a new tab) that, if select, would have a probe launched in 2031 to study Triton, before annihilating flying in the atmosphere of Neptune.
The planned missions to Venus and Titan over the next decade will revolutionize our understanding of these two. NASA’s Dragonfly mission (opens in a new tab), scheduled to leave Earth in 2027 and reach Titan in 2034, will land an unmanned helicopter in the dunes of the Moon.
Pluto was observed during a 2015 flyby (opens in a new tab) by NASA’s ongoing New Horizons mission, but there are no plans to return.
This article is republished from The Conversation (opens in a new tab) under a Creative Commons license. Read the original article (opens in a new tab).
Follow all Expert Voices topics and discussions (and be part of the discussion) on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher.