Although there is so much speculation on alien life outside Earth, there is no concrete proof that extraterrestrial life exists. Australian National University (ANU) astronomers believe climate change has something to do with their possible death as well as other planets.

Discovery of planets beyond those identified in the Milky Way has captured the imagination of the science community following the discovery by Caltech researcher of Planet 9. Aditya Chopra, lead author of the ANU study, published in the Astrobiology journal, writes that the universe is “probably filled with habitable planets,” which explains the belief by many scientists that these planets should have inhabitants whom Earthlings refer to as “aliens.”

He believes that because of the fragile environment of early life in the universe, the evolution was so fast that some planets and its inhabitants possibly did not survive. Because most early planetary environments were unstable, life forms require regulation of greenhouse gases, such as water and carbon dioxide, to keep surface temperatures stable and produce a habitable planet.

But because these planets would likely not find that balance, unlike Earth, it could have been burned by greenhouse effect as scientists think what happened to Venus or frozen by the thinning environment similar to Mars. The ANU astronomers add that Earth exist at “just the right spot around a stable star” to spawn life and stabilise the atmosphere in the last 4 billion years.

Chopra points out, “The mystery of why we haven’t yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces.”

The researchers add that while there are plenty of potential exoplanets with similarities to Earth, its having Earth-like features does not necessarily mean these planets have environmental conditions conducive to life that Earth possesses.

The researchers call their theory the Gaian Bottleneck Hypothesis, reports Gizmondo. The hypothesis states life in other planets existed, but only a short period and went extinct quickly. But Gizmondo doubts the hypothesis because of the likely existence of billions of potentially habitable planets in the galaxy which has sustained life for more than 5 billion years, making the Gaian hypothesis “one hell of a bottleneck.”