Astronomy: Interstellar cloud could have triggered the current ice age
Two to three million years ago, important changes took place on Earth that are still having an effect. An astronomer may have an explanation.
(Image: m.elyoussoufi/Shutterstock.com)
A few million years ago, our solar system moved through an interstellar cloud of dense gas and dust, which compressed its protective bubble to such an extent that the Earth was directly exposed to the interstellar medium and may have fallen into the most recent ice age as a result. This is at least the theory now published by astronomer Merav Opher from Boston University. Together with two colleagues, she has determined that the encounter with a long gas cloud system two to three million years ago may have caused the so-called heliosphere, which currently extends to a distance of well over 100 astronomical units (AU), to be compressed to just 0.2 AU. This is within the orbit of Mercury. On Earth, the lack of protection could have led to substantial changes, for example in the climate.
Influence on the emergence of humans?
The analysis was made possible by the extensive data collection of the European Gaia space telescope, which creates a precise 3D map of celestial bodies and objects such as the LRCC (Local Ribbon of Cold Clouds) cloud system. Opher and her team used this to recalculate the path of our solar system and found the contact. Further simulations would then have revealed what effects the encounter had on the heliosphere. This is formed by the solar wind, which normally pushes so strongly against the interstellar medium that large areas of the solar system do not come into contact with the material between the stars. According to the calculations, however, the comparatively dense material of the interstellar cloud has compressed it so strongly that it has also reached the inner planets.
What effects this contact had on the Earth and its climate, for example, still needs to be investigated, writes Opher. However, it is clear that the comparatively large quantities of neutral hydrogen in the gas cloud may have changed the chemistry of the Earth's atmosphere. According to theories, this could have removed the ozone layer from deeper layers and ultimately caused the Earth to cool down. It has also been discovered that more radioactive particles reached the Earth's surface at that time. Finally, the research group also points out that the genus of apes from which modern humans eventually evolved also emerged around this time. Apart from this temporal proximity, however, the group has no evidence of a connection.
Overall, the simulations suggest that the Earth was directly exposed to the interstellar medium for between a few hundred thousand and a million years as it moved through the interstellar cloud. The astronomer admits that it is currently impossible to find out the exact consequences. Nevertheless, the temporal proximity to important events in the Earth's recent history is likely to attract a great deal of attention to the study; Opher herself would like to see more research on this and says that we are at the very beginning. This is not the first paper to point out the influence that the sun's path through the Milky Way has had on the Earth. The latest research paper has now been published in the scientific journal Nature Astronomy, and the now controversial astrophysicist Avi Loeb also contributed to it.
(mho)