Despite the first sprouts of life, ancient Land was not the most pleasant place. The surface of the planet regularly pobivali space rocks, the atmosphere did not contain oxygen and, consequently, had no ozone to protect the surface from exposure to UV radiation. In addition, young the Sun was made 25% less energy than today, bringing the average temperature on the Earth near the surface had to be below the freezing point of water.

But it there was not. Geological data indicates the existence of liquid oceans soon after the formation of the planet, and the first one and a half billion years of Earth's history has left us with traces of glaciation. This puzzle is a paradox faint young Sun - the first in 1972, was described by Carl Sagan and George Mullen.

Young sun-like star 1RXS J160929.1-210524 and its planet (image Gemini Observatory, D. Lafreniere, R. Jayawardhana, M. van Kerkwijk / Univ. Toronto).

Since then a lot of hypotheses. Some believe that the Earth had less reflective because of the lack of continents and reduced cloud cover, resulting absorb more sunlight. Others put on greenhouse gases. Much effort spent on the calculation of CO2, methane and more exotic compounds like carbonylchloride (OCS) in the ancient atmosphere, which, incidentally, was more likely, then, every year, which increased the efficiency of greenhouse gases.

The combination of these factors are enough to solve the paradox, but neither is a lot of details. Robin Wordsworth and Raymond Perambur of the University of Chicago (USA) offer a link to another piece of the puzzle to the interaction in the atmosphere of hydrogen and nitrogen.

Neither one (H2) no other (N2) separately is not a greenhouse gas, that is not absorb infrared radiation emitted by the planet (this fact is determined by their molecular structure). However, when they collide strange things happen. For a moment they start to behave like one big molecule greenhouse gas. This process, by the way, plays an important role in the energy balance of the satellite of Saturn the Titan.

Until recently it was believed that the early earth's atmosphere was very little hydrogen, because it costs nothing to fly in space thanks to its low weight. But now it is proved that the loss rate this item was written in ancient times it was present in significant numbers.

The authors of a new study has calculated that the above collision could heat the Earth by as much as 10-15 C. If this is true, then even a moderate influence of other factors would be more than enough to planet from freezing. (However, one of the recent works have shown that young the Sun was given even less heat, so other factors might be needed to complete.)

Obviously, the absorption of infrared radiation in this way has played an important role only as long as the atmosphere was rich in hydrogen. Everything changed once at the stage bacteria that process the carbon dioxide and hydrogen into methane and water. Methane absorbs infrared radiation only at a certain wavelength, and so on reaching a certain concentration additional contribution of methane in the greenhouse effect becomes insignificant. Methanogens are probably very quickly reached this point, then the consumption of carbon dioxide and hydrogen began to give the rest a cooling effect. In addition, the high concentration of methane was to lead to the formation of haze reflecting sunlight.

Therefore, the researchers suggest that extensive glaciation that occurred about 2.9 billion years ago, could be due, ironically, biological production of methane. There are still many unknowns, so space for research.

In comments to the article with the results of the research of James Casting from the University of Pennsylvania (USA) noted that the conclusions colleagues have extraterrestrial value. If H2 is indeed able to heat the planet of the earth type, it becomes possible for life to exist on the same young planets (including on ancient Mars), located ten times further from the sun-like star than the Earth.

The study is published in the journal Science.

Prepared according to Ars Technica.