A new study published in Science reveals that gullies on Mars could have been carved when the planet was significantly tilting to its side. This tilter could have enabled intense climate change that led to water flowing down the slopes of the Red Planet.
Gullies on Mars
The Red Planet's gullies were first discovered by scientists in the year 2000, Space.com reports. They strikingly resemble the channels that form in Antactica's Dry Valleys, which are carved by water that cascades from glaciers that are melting.
The ravines suggest that water could have once cascaded on the Red Planet. They also show the possibility of this happening from time to time.
Planetary scientist James Dickson, who is from the California Institute of Technology, explains that these gullies appear Earth-like. However, they are on Mars. He questions how these ravines could have formed on the Red Planet. The scientist adds that this puzzle has been the focus of several scientists.
The issue with these Martian gullies is that such ravines are typically situated at heights where fluid water is not expected to be present, given the climate of the Red Planet. Space.com adds that the planet's air is too thin and cold for liquid water to last a while. Moreover, these levels are even thinner and colder at higher altitudes.
Caused by Cascading Water?
While other possible explanations have been posited, the scientists wanted to see if fluid water could have existed on the planet. They examined the change in the Red Planet's axial tilt and its effects. Space.com explains that with more planetary poles tilted with respect to its solar orbit, the higher the variation in sunlight exposure in different areas of the planet for its own year course.
On Earth, the axial tilt is roughly 23.5 degrees. This leads to seasonal changes. As for Mars, the axial tilt lies at around 25 degrees, but has varied from 15 to 35 degrees in the past hundreds of thousands of years. This allows for dramatic climate changes.
Chemistry World explains that Dickson and his colleagues modeled the solar orbit of the planet at a 35-degree axial tilt. They discovered that in the particular Martian regions where the gullies are situated, sublimating ice carbon dioxide would have led to significant density in the Red Planet's atmosphere. On top of this, the surface temperatures would have surpassed water ice's melting point. Space.com further explains that such conditions could have repeatedly happened in the last several million years, with the most recent one occurring roughly 630,000 years ago.
On top of this, the gullies on Mars currently have significant water ice close to their surface. It is likely that it has had even more water ice in the past million years. The authors suggest that when the axial tilt was high, huge quantities of this ice could have melted to carve out the Martian gullies.
Overall, the authors propose that melting ice, carbon dioxide sublimation, and high axial tilt all work together to explain the gullies on Mars.
Dickson explains that a vital implication of such notions is that when the orbit of Mars ends up tilting again, it should lead to meltwater in the specific location of the gullies.
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