A study conducted by geologists at Brown University (Rhode Island) provides a possible compatibility between the warm and humid scenario that follows from the Martian geology and cold and frozen past suggested by some atmospheric models.
Even assuming that Mars is generally frozen, the research reveals that it is feasible that daily maximum temperatures in summer could rise above freezing enough to contribute to melting ice at the edges of glaciers.
That meltwater, poured in relatively small amounts year after year, could have been enough to sculpt the characteristic canals and channels of erosion that are observed in the red planet today, according to the researchers, who have published their online study in Icarus magazine .
The lead authors are Ashley Palumbo, a student at Brown University, Jim Head, a professor in the Department of Earth Sciences, Environmental and Planetary Brown, and Robin Wordsworth, a professor at the Harvard School of Engineering and Applied Science.
According to Palumbo, the research was inspired by the Earth‘s climate dynamics, particularly in Antarctica: “In the Dry Antarctic Valleys we can see a similar phenomenon, because the seasonal rise in temperature is enough to form lakes and keep them liquid, weigh that the average annual temperature is well below the freezing point, so we wanted to see that something like that could have been produced on Mars millions of years ago.”
The researchers came from a cutting-edge climate model for the red planet, which imagines an atmosphere composed largely of carbon dioxide (as it is today).
That scenario gives rise to a primitive cold and icy Mars, partly because it is believed that solar energy production was much weaker in the early history of the solar system.
The researchers executed the model taking into account a wide range of parameters for variables that might have been important about 4,000 million years ago, when the network of riverbeds and valleys in the southern highlands of the planet formed.
Although scientists generally agree that the atmosphere of Mars was denser in the past, it is unclear what its real thickness was.
Likewise, while most experts agree that the atmosphere was mainly carbon dioxide; small amounts of other greenhouse gases may be present. Palumbo and his colleagues analyzed the model with several feasible atmospheric thicknesses and with additional degrees of warming from the greenhouse effect.
It is also not known precisely what the variations in the orbit of Mars would be 4,000 million years ago , so the researchers tested a number of plausible orbital scenarios. They also tested different degrees of axis tilt, which influences the amount of light solar that receive the upper and lower latitudes of the planet, as well as in different degrees of eccentricity, ie the distance at which the planet’s orbit deviates from the circle, which can increase seasonal temperature changes.
The study envisioned scenarios where ice covered the region close to the current location of the valley networks. While the annual mean temperature of the planet in these scenarios remained well below the freezing point, the model produced maximum summer temperatures in the southern highlands that rose above the freezing point.
In order to be able to explain the visible traces of water flowing from this mechanism, it is necessary that the volume of water in the time duration of the formation of the network is enough so that the water comes to the surface at required speeds to carry out an erosive action.
A few years ago, Jim Head and Brown Eliot Rosenberg University student published an estimate of the minimum amount of water needed to carve the largest of the valleys. Using that as a guide, along with estimates of required runoff rates and duration of the network formation of other study valleys.
Palumbo showed that in the case in which the Martian orbit was highly eccentric met these criteria. That required degree of eccentricity is within the range of possible orbits for Mars 4,000 million years ago. Together, according to Palumbo, the results provide a scenario that makes compatible the geological evidence of water flowing in early Mars with the atmospheric evidence of a cold and icy planet.