It is expected that as the Sun travels through the interstellar medium, there will be different conditions affecting the shape, size and nature of the Heliosphere. Recently Prof. Opher investigated the conditions of the Heliosphere 2-3Million years ago.
Although the interaction with molecular clouds was previously considered, the terrestrial impact of compact cold clouds was neglected. There is geological evidence from 60Fe and 244Pu isotopes that Earth was in direct contact with the ISM 2-3 million years ago. Prof. Opher and collaborators show that the solar system may have passed through the Local Ribbon of Cold Clouds within 1-sigma, 2 Million years ago. Under the conditions of the encounter the heliosphere shrunk to a scale smaller than the Earth’s orbit around the Sun. The Earth was exposed to a neutral hydrogen density of up to 3000cm-3. Prof. Opher is exploring the effects of that exposure to Earth’s climate and potentially on human evolution at that time, as suggested by existing data.
She is extending this study to farther distant times as 7 Million years ago when the Heliosphere was in contact with the edge of the Local Bubble.
Selection of Prof. Opher’s most significant papers on the subject:
Opher, M., Loeb, A., Peek, J. “Evidence that Earth was exposed to Cold Dense Interstellar Medium 2 Myrs Ago”
Opher, M. Loeb, A., Zucker, C., Goodman, A., Worden A. Alves, J., “Consequences of the Encounter of the Heliosphere with the Edge of the Local Bubble”