NASA study links recurring interstellar cloud encounters to Earth's ice ages
This digest was compiled by AI from multiple sources — links to the originals are below.
NASA's SHIELD center research shows the solar system passed through dense interstellar clouds at least three times in the last 14 million years, compressing the heliosphere and exposing Earth to interstellar material. The findings match geological evidence from deep-sea cores, Antarctic snow, and lunar samples. The study suggests these encounters may have triggered ancient climate shifts, including ice ages.
Key Facts
- The heliosphere normally extends about 11 billion km from the Sun, far beyond the outer planets.
- During one modeled encounter, the heliosphere shrank to 0.22 astronomical units, smaller than Earth's orbit.
- The encounters occurred approximately 2–3 million, 6–7 million, and 13–14 million years ago.
- Interstellar dust elements were found in deep-sea sediment cores, Antarctic snow, and lunar samples from those periods.
Heliosphere Compression
The heliosphere is a protective bubble formed by the solar wind that shields the planets from interstellar radiation. Its outer boundary normally lies about 11 billion km from the Sun, beyond the orbits of the outer planets. When the solar system passes through dense clouds of cold hydrogen gas, external pressure can compress the heliosphere inward. Modeling showed that during one such passage the heliosphere contracted to 0.22 astronomical units, less than the radius of Earth's orbit. This compression would have brought Earth into direct contact with the dense interstellar medium.
Geological Evidence
Researchers found elements characteristic of interstellar dust in deep-sea sediment cores, Antarctic snow, and lunar samples. These findings correspond to the periods of the modeled encounters: 2–3 million, 6–7 million, and 13–14 million years ago. The study suggests that passages through colder galactic regions may have influenced ancient climate changes, including possible ice ages.
1 source
NASA study links recurring interstellar cloud encounters to Earth's ice ages
