This article was originally published in The Conversation. (opens in a new section) The publication contributed to the article in Expert Voices on Space.com: Op-Ed & Insights.
Andrew Gunn (opens in a new section), Lecturer, Monash University
What is it like to be on the surface of Mars or Venus? Or even further, such as Pluto or Saturn’s moon Titan?
This curiosity has contributed to advances in space exploration since the launch of Sputnik 1 65 years ago (opens in a new section). But we are just beginning to scratch the surface of what is known about other planetary bodies in the solar system.
Our new study (opened in a new section), published May 19 in Nature Astronomy, shows how some unlikely candidates – namely sand dunes – can give an idea of what time and conditions you may experience if you stand on a distant planet. body.
Related: Strange “blue” dunes streak the surface of Mars in a NASA photo
What’s in the sand?
The English poet William Blake wondered (opens in a new section) what it meant to “see the world in a grain of sand.”
In our study, we took this quite literally. The idea was to use the very presence of sand dunes to understand what conditions exist on the surface of the world.
In order for dunes to exist, there are two criteria “Goldilocks (opens in a new section)” that must be met. The first is the supply of eroding but durable grains. There must also be fast enough winds to make these grains bounce on the ground – but not fast enough to carry them high into the atmosphere.
Until now, direct measurements of winds and sediments have only been possible on Earth and Mars. However, we observed wind-blown sediments on many other bodies (and even comets (opens in a new section)) via satellite. The very presence of such dunes on these bodies suggests that Goldilocks’ conditions were met.
Wind elements of (top left, clockwise) Earth, Mars, Titan, Venus, Pluto and Triton were captured by satellites. (Image Credit: Nature Astronomy / Image adapted from Gunn and Jerolmack (2022))
Our work focuses on Venus, Earth, Mars, Titan, Triton (Neptune’s largest moon) and Pluto. Unauthorized debates about these bodies have been going on for decades.
How do we compare the visible, wind-blown characteristics of Triton’s and Pluto’s surfaces with their thin, faint atmospheres? Why do we see such fruitful activity on the sand and dust of Mars, despite measuring winds that seem too weak to sustain it?
And does the dense and suffocatingly hot atmosphere of Venus move sand in a similar way as air or water move on Earth?
Continuation of the debate
Our study provides estimates of the winds needed to move sediment to these bodies, and how easily this sediment will disintegrate in these winds.
We built these predictions by putting together the results of many other research papers and testing them against all the experimental data we could get our hands on.
We then applied the theories to each of the six bodies, using telescopic and satellite measurements of variables, including gravity, atmospheric composition, surface temperature, and sediment strength.
Studies before ours have looked at either the wind speed threshold needed to move sand, or the strength of various sediment particles. Our work combines them together – seeing how easily particles can disintegrate when transporting sand on these bodies.
The wind-blown waves of the Bagnold dunes on Mars were captured by the Mars rover Curiosity. (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 fog (opens in a new section) that rains from the atmosphere, or is it mixed with thicker ice?
As it turned out, we found that the loose aggregates of organic mist would disintegrate in a collision if blown by the winds on the equator of Titan.
This suggests that Titan’s dunes are probably not made of pure organic fog. In order to build a dune, the sediment must be blown away by the wind for a long time (some of the sands of the Earth’s dunes are a million years old (opens in a new section)).
We also found that wind speeds must be too fast on Pluto to transport methane or nitrogen ice (which was supposed to represent the sediments of Pluto’s dunes). This calls into question whether the “dunes” in Pluto’s plane, Sputnik Planitia (opens in a new section), are dunes at all.
Instead, they can be sublimation waves (opens in a new section). These are dune-like relief forms made by sublimation of material instead of erosion of sediments (such as those observed on the northern polar cap of Mars).
Our results for Mars suggest that more dust is generated from the wind-blown sand on Mars than on Earth. This suggests that our models of the Martian atmosphere may not be able to effectively capture the strong “catabatic” winds on Mars, which are cold gusts that blow down at night.
Potential for space exploration
This study comes at 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 on site. Studies like ours help to inform the goals of these missions and the paths taken by rovers such as Perseverance (opens in a new section) and Zhurong (opens in a new section).
Within the outer limits of the solar system, Triton has not been observed in detail since the spring of NASA Voyager 2 in 1989. There is currently a mission proposal (opens in a new section), which, if selected, will have a probe launched in 2031. studied Triton before being destroyed by flying into the atmosphere of Neptune.
Planned missions to Venus and Titan over the next decade will revolutionize our understanding of the two. NASA’s Dragonfly mission (opening in a new section), which is due to leave Earth in 2027 and arrive on Titan in 2034, will land an unmanned helicopter on the dunes of the moon.
Pluto was observed during a flyover in 2015 (opens in a new section) by NASA’s current mission New Horizons, but there are no plans to return.
This article has been republished by The Conversation (opens in a new section) under a Creative Commons license. Read the original article (opens in a new section).
Follow all the questions and debates of Expert Voices – and become 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.
Add Comment