The Solar System is not static; it moves around the Milky Way. Occasionally, they cross regions of denser interstellar medium. The impact of these clouds of hydrogen and other materials on the Solar System and our planet is not fully understood, but there is a possibility that the clouds of interstellar gas may have triggered an ice age.
Previous research, published earlier this year, suggests that the Solar System crossed a dense interstellar cloud 2 million years ago, which may have caused an ice age. Later work identified another possible example, this time 7 million years ago, but the effects of that encounter would have been more complex.
“This cloud was long in our past, and if we crossed something this massive, we were exposed to the interstellar medium,” , a space physicist at Boston University (USA).
A walk of the planet through space
This is the essence of the event: the interstellar cloud affected the bubble of , the heliosphere. The new research suggests that the two encounters, first with the edge of the Local Bubble (7 million years ago) and then with the Cold Cloud in the Constellation Linx (2 million years ago), brought a large amount of hydrogen into the upper atmosphere.
This interstellar hydrogen, combined with , would have formed water. The oxygen would have come from ozone, causing a localized depletion of it, in some cases by up to 99%. The presence of water in larger amounts at high altitudes could have led to the formation of a greater number of noctilucent clouds, sparse and thin clouds that form at about 76 – 85 kilometers altitude.
Have interstellar gas clouds affected Earth’s climate?
These newly formed clouds would not have been sparse and thin, but thick; and here comes the climate question. could it have affected the upper atmosphere, but could it have caused an ice age? The answer is still uncertain. The presence of noctilucent clouds could have reflected more sunlight, but they could have also trapped more heat from the ground. Other factors that may have contributed, such as increased cosmic rays and other phenomena, could mean that this event did not produce a clear cooling or warming.
The research team suggests that more detailed 3D atmospheric models could solve the mystery, but the influence may not be so clear and no evidence can be found in the geological record that Earth and the Solar System passed through these clouds. .
The study was published in .
