This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: At the center of our solar system, the sun influences every planet that orbits it. In two recent studies, scientists uncovered how ancient events in the sun's history may have helped create Earth's unique climate and driven previously unexplained climatic shifts.
In new research, scientists at NASA's SHIELD (Solar Wind with Hydrogen Ion charge Exchange and Large-Scale Dynamics) center—one of NASA's DRIVE (Diversify, Realize, Integrate, Venture, Educate) Science Centers—trace the trajectory of the heliosphere, the massive bubble created by our sun that envelops our solar system, as it moved through our galaxy and influenced Earth's climate along the way. In another paper, a NASA scientist and co-authors investigate how the younger, dimmer sun managed to heat Earth by seeding the production of potent greenhouse gases. Over the last tens of millions of years, Earth's climate has undergone significant shifts, including notable ice ages in which the global average temperature temporarily dropped by several degrees.
During these periods, more frequent climate swings caused Earth to warm and cool. To explain these periods of warming and cooling, scientists looked to factors internal to Earth, including orbital changes, greenhouse gases and ice. But new research suggests changes to the sun's environment may be key to understanding Earth's temperature swings.
Just as our planet is encased by an atmosphere, so our entire solar system is encased inside a kind of "atmosphere" created by the sun. This protective bubble, known as the heliosphere, is formed by a continuous solar wind of charged particles streaming out from the sun in all directions. Our heliosphere orbits around the center of our galaxy, the Milky Way.
Throughout the sun's 4.6-billion-year existence, our heliosphere has traversed various regions within our galaxy. In a paper published Aug. 21 in the Annual Review of Astronomy and Astrophysics, researchers at NASA's SHIELD used computer modeling to reverse-engineer the path of the heliosphere through our galaxy, revealing that the environments it passed through may have triggered changes on Earth. Merav Opher, SHIELD's principal investigator at Boston University, and her team ran simulations that showed the sun has encountered frigid expanses of gas and dust at least three times in the past few million years.
In these instances, massive interstellar "cold clouds" pushed against the heliosphere to such an extent that it shrank to smaller than Earth's orbit, stranding our planet outside the sun's protective shield. These exposures—approximately 2–3 million years, 6–7 million years and 13–14 million years ago—would have exposed Earth's atmosphere to different surroundings. The simulation results match geologic evidence: Elements prevalent in interstellar dust appear in deep-sea sediment core samples, Antarctic snow and lunar samples from these periods.
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