What is it like to be on the surface of Mars or Venus? Or even further, like on Pluto, or Saturn’s moon Titan? This curiosity has made progress in space exploration since Sputnik 1 was launched 65 years ago.
But we’re only beginning to scratch the surface of what’s worth knowing about other planetary bodies. The Solar System,
Our new studyPublished today in Nature Astronomy, shows how some unlikely candidates — namely sand dunes — could provide insight into what weather and conditions you might experience if you were to stand on a distant planetary body.
What’s in a grain of sand? The English poet William Blake famously wondered what it meant to “see the world in a grain of sand”.
In our research, we took it quite literally. The idea was to use only the presence of sand dunes to understand what conditions exist on the surface of the world.
For dunes to exist, there are a pair of “Goldilocks” criteria that must be satisfied. The first is the supply of erasable but sustainable grains.
Winds must also be strong enough to toss those grains onto the ground – but not strong enough to lift them high into the atmosphere.
So far direct measurement of winds and sediment has been possible only at Earth And Mars planet,
However, we have seen features of wind-blown sediment on many other objects (and even comets) by satellite.
The presence of such mounds on these bodies means that Goldilocks conditions are met.
Our work focuses on Venus, Earth, Mars, Titan, Triton (Neptune’s largest moon) and Pluto. The unresolved debate about these bodies has gone on for decades.
How do we square off the apparent wind-blown features on the surfaces of Triton and Pluto with their thin, weak atmospheres? Why do we see so much profuse sand and dust activity on Mars, despite measuring winds that seem too weak to sustain it? And does Venus’s dense and hard warm atmosphere move sand in the same way that wind or water moves on Earth? Furthering the debate, our study provides predictions for the winds needed to move sediment over these bodies, and how easily sediment will break down in those winds.
We made these predictions by piecing together the results of several other research papers and testing them against all the experimental data we could get our hands on.
We then applied the principles to each of the six bodies, drawing on telescope and satellite measurements of variables including gravity, atmospheric composition, surface temperature and sediment strength.
Our earlier studies have looked at either the wind speed range required to move the sand, or the strength of the various sediment particles.
Our work pieced these together – looking at how easily the particles can break down during sand-transport weathering on these bodies.
For example, we know that Titan has sand dunes at its equator – but we can’t be sure which sediment circles the equator.
Is it pure organic haze raining down from the atmosphere, or is it densely mixed with snow? As it turns out, we found that loose aggregates of organic haze would disintegrate upon collision if they were blown away by winds at Titan’s equator.
This means that Titan’s mounds may not have been entirely composed of organic haze. In order to form dunes, sediment must be blown around in the wind for a long period of time (some of Earth’s dune sands are a million years old).
We also found that the wind speed must have been extremely fast to transport methane or nitrogen ice on Pluto (which was hypothesized to be Pluto’s dune sediments).
This raises the question of whether the “dunes” on Pluto’s plain, Sputnik Planitia, are dunes.
They may instead be sublimation waves. These are dune-like landforms formed by the sublimation of material rather than by sediment erosion (as seen on the north polar cap of Mars).
Our results for Mars suggest that wind-borne sand transport generates more dust on Mars than on Earth.
This suggests that our models of the Martian atmosphere are not able to effectively capture the strong “catabetic” winds of Mars, which are cold winds that blow downward at night.
This study comes at an interesting stage in space exploration.
For Mars, we have a relative abundance of observations; Five space agencies are operating missions in orbit or in situ. Studies like ours help inform the objectives of these missions and the paths taken by rovers like Perseverance and Jurong.
In the outer reaches of the Solar System, Triton has not been observed in detail since the NASA Voyager 2 flyby in 1989.
There is currently a mission proposal which, if chosen, would launch a probe in 2031 to study Triton before destroying itself by flying into the atmosphere of Neptune.
Planned missions to Venus and Titan in the coming decade will revolutionize our understanding of both.
of nasa The Dragonfly mission, set to leave Earth in 2027 and arrive at Titan in 2034, will land an unmanned helicopter over the moon’s dunes.
Pluto was seen during a 2015 flyby by NASA’s ongoing New Horizons mission, but there are no plans to return.