Colossal solar storms may have made ancient Earth habitable
According to a new NASA study, powerful solar storms could have been instrumental in warmingancient Earth, and preparing the planet for the development of complex life. Known as "superflares,"the space weather events were thought to be roughly 10 times morepowerful than any solar storm that has struck Earth since the adventof modern civilization.
Astronomers are able to piece together the history of our Sun byanalyzing similar main sequence stars in the various stages of theirevolutionary cycle, through powerful telescopes such as Hubble and Kepler.
From these observationswe can tell that around 4 billion years ago when life first began,the Sun shone only two thirds as bright, and provided only 70 percentof the energy as it does today. These stellar conditions should haverendered Earth an icy, inhospitable world, yet we know fromgeological records that this was not the case.
New research suggeststhat our planet and the Sun boasted complementary traits that allowedearly life to be nurtured and incubated even as the two celestialbodies matured. Current-day Earth generates a strong magnetic fieldcapable of deflecting the majority of the stellar material flung at itthrough events such as a coronal mass ejections.
However, 4 billionyears ago Earth's magnetic field was much weaker, especially around the polar regions. At the same time, while the overall output of our Sun waslower than it is today, observations made by Kepler of Sun-like starsof an age with ancient Earth suggests that it generated powerful solar storms knownas superflares on a regular basis.
Energetic particlesfrom the superflares may have traveled down magnetic field lines, enteringEarth's atmosphere through the polar regions. Once in Earth's atmosphere, the stellar particles broke downnitrogen molecules creating vast quantities offree-floating nitrogen particles, which combined with oxygen to formnitrous oxide.
Nitrous oxide is apowerful greenhouse gas up to 300 times more effective as anatmospheric warming catalyst than carbon dioxide. A relatively tinyamount of nitrous oxide could have trapped enough of the Sun's energyinside ancient Earth's atmosphere to create warm surface conditionsfavourable to the evolution of life.
The energy provided bythe charged particles may have provided the boost needed for simplemolecules to combine to form complex molecules such as DNA and RNA.Insights into how Earth became an ideal breeding ground for lifewill directly aid the search for its extraterrestrial counterpart.
Astronomerscan now search for Earth-like planets with relatively weak magnetic fields orbiting in the habitable zone of stars exhibiting superflares, in the knowledge that these are promising signs of a youngworld capable of playing host to life.