On Mount Sharp, near Gale crater on Mars, there is a layer of rocks that differs from the rest in color and density. All scenarios of its formation known to scientists assume the presence of water. It is possible to check which one is correct when Curiosity gets there.
Mysterious Marker Layer
Mount Sharp is an elevation on Mars that rises 5.5 kilometers above the surrounding surface. Since it is the central peak of Gale Crater, in which the Curiosity rover operates, quite a lot is known about it. However, this geological formation has one mystery that interests scientists very much, and they hope to find an answer to it soon.
The images of the orbiters and Curiosity on the mountainside clearly show a layer of dark knife rock above and below the material. It also has a different texture and looks stronger than other stones.
Geologists call such layers marker horizons. Usually, their presence is associated with certain global events that can be dated. Due to this, the time of formation of other rocks is counted by them on Earth.
On Mount Sharp, this marker layer varies in height by 1.6 km and has a slope of 1-5 degrees. In its chemical composition, it is similar to other sulfate-bearing rocks in Gale Crater, but differs from them in its physical characteristics.
What changed the rocks in Gale Crater
It is obvious that the reason for the appearance of the marker horizon was some event that changed the nature of rock formation in Gale crater. What kind of event it was, scientists are not sure, but they have three possible scenarios of events. The first of them implies the presence at the time of formation of a layer of water in which certain chemicals were dissolved. These substances got inside the layer and led to its cementation.
The second possibility is that the horizon, on the contrary, is sandstone, which was formed in conditions when the Gale crater was drier than when sulfates were formed in it. The third possibility is that the cementation was caused by volcanic ash deposited on the surface of the crater.
All three scenarios assume a change in humidity in the crater over a long time. And this does not agree very well with the picture of the past of Mars, which has been in a dry state for billions of years. However, scientists assume that a mechanism is responsible for the formation of the marker horizon, which they have not yet seen on Earth.
In any case, only the Curiosity rover will be able to clarify the situation. It is already 700 meters away from the marker layer, and it has all the necessary instruments. Scientists will finally be able to find out what happened in Gale Crater in the past.
According to phys.org
Follow us on Twitter to get the most interesting space news in time