Mars
Portions of the Martian surface shot by NASA's Mars Reconnaissance Orbiter show many channels from 1 meter to 10 meters wide on a scarp in the Hellas impact basin, in this photograph taken January 14, 2011 and released by NASA March 9, 2011. Scientists have found the first evidence that briny water may flow on the surface of Mars during the planet's summer months, a paper published on Monday showed. Researchers found telltale fingerprints of salts that form only in the presence of water in narrow channels cut into cliff walls throughout the planet's equatorial region. Reuters

A research conducted by the scientists at the Brown University has found that liquid water flowed on the surface of Mars four billion years ago. The study also revealed that there were climate changes on Mars which were similar to that on the Earth.

According to the new study titled "Late Noachian Icy Highlands Climate Model: Exploring the Possibility of Transient Melting and Fluvial/Lacustrine Activity Through Peak Annual and Seasonal Temperatures", which was published in the Journal Icarus, water existed in forms of ice and as liquid water on the surface of the Earth.

The research was done by Ashley Palumbo, a Ph.D. student of the Brown's Department of Earth, Environment and Planetary Science, her supervising professor, Jim Head and Prof. Robin Wordsworth of Harvard University's School of Engineering and Applied Science.

The study has found that the red planet's surface was once warm and wet while its atmosphere remained cold. Water was present in the form of glaciers which melted during the summer. It flowed through the surface to form canals, valleys and other features which are more common in the Mars Southern highlands.

Ashley Palumbo, who led the research said, "We see this in the Antarctic Dry Valleys, where seasonal temperature variation is sufficient to form and sustain lakes even though the mean annual temperature is well below freezing. We wanted to see if something similar might be possible for ancient Mars."

Palumbo started her study with the state-of-the-art climate model for Mars which states that Martian atmosphere was primarily composed of carbon dioxide, which is the same even today, and the Sun's temperature was much lesser. They assumed that Mars was generally cold and icy during those days.

According to the theory, the Martian atmosphere was thicker during those days and might have resulted in the significant rates of the greenhouse effect. The researchers, however, couldn't reach a final conclusion regarding the thickness of the planet's atmosphere during the period which was 4.2 and 3.7 billion years ago.

The research also found the possibility of tilts formed in the planet's axis through decades which might have resulted in the difference in the amount of sunlight received. The Marian orbit has been believed to have changed significantly adding to the seasonal changes in the planet. The seasonal changes had significantly contributed to the temperature of the planet.

The Martian model studied has also shown wide disparities in the surface temperature of the red planet. It theorized scenarios of both freezing temperatures and summers which melted ice to water. The volume of water produced by ice melting had been already estimated by an earlier study in 2015, by Prof. Jim Head and Eliot Rosenberg. This study had also helped the team to make a hypothesis.

Ashley Palumbo said, "This work adds a plausible hypothesis to explain the way in which liquid water could have formed on early Mars, in a manner similar to the seasonal melting that produces the streams and lakes we observe during our field work in the Antartic McMurdo Dry Valleys. We are currently exploring additional candidate warming mechanisms, including volcanism and impact cratering, that might also contribute to melting of a cold and icy early Mars."

However, there were debates such as how running water was possible on the planet during the time when the sun's temperature was much weaker. However, it acts as a bridge between ideas of "warm and watery planet and the "cold and icy" planet theories.