Cumulative evidence shows that during the ancient Noachian period time, the surface environment of Mars had liquid water and may have been habitable for microorganisms. The existence of habitable conditions does not necessarily indicate the presence of life.
After mapping cosmic radiation levels at various depths on Mars, researchers have concluded that over time, any life within the first several meters of the planet’s surface would be killed by lethal doses of cosmic radiation. By the mid-19th century, astronomers knew that Mars had certain other similarities to Earth, for example, that the length of a day on Mars was almost the same as a day on Earth.
A study lead author Lujendra Ojha said, “Even if greenhouse gases like carbon dioxide and water vapor are pumped into the early Martian atmosphere in computer simulations, climate models still struggle to support a long-term warm and wet Mars.” “I and my co-authors propose that the faint young sun paradox may be reconciled, at least partly, if Mars had high geothermal heat in its past.” He also added, “The new study, which was published online in the journal Science Advances, could have applications beyond the Red Planet. For example, the faint young sun paradox complicates our understanding of life’s emergence on the early Earth. Radiogenic heat may have played a large role in making our planet habitable long ago.”