.Title: Galactic encounters and ice ages in the earth's history
Author(s): Sankaran AV
Source: CURRENT SCIENCE 89 (3): 439-440 AUG 10 2005
Document Type: Editorial Material
Language: English
Cited References: 9 Times Cited: 0
Now a team of astrophysicists, atmosphere and space physicists has found galactic
involvement for the repeated development of ice ages on earth According to their
postulate, whenever the solar system while orbiting around the centre of our Milky
Way galaxy, once in 250 million years, encounters giant molecular clouds (GMC),
dramatic changes in climate could be triggered on earth. Several thousands of such
cloud masses, mostly made up of atomic and molecular hydrogen and dusty carbonaceous particles and silicates are known to lie in its path (Figure 1). They can effectively shut-off solar radiation, enhance water vapour content of the middle atmosphere with attendant drop in temperature, form dense mesospheric ice-clouds and
finally precipitate runaway ice-albedo feedback leading to global cooling8. A mere 5
to 10% reduction in the solar luminosity by the dust could decrease the amount of
heat reaching earth and initiate sufficient cooling for the polar ice to spread slowly
to low latitudes and even up to the equator
Galactic encounters and ice ages in the earth's history??
Moderator: Moderators
Galactic encounters and ice ages in the earth's history??
Title: Passing through a giant molecular cloud: "Snowball" glaciations produced by interstellar dust
Author(s): Pavlov AA, Toon OB, Pavlov AK, Bally J, Pollard D
Source: GEOPHYSICAL RESEARCH LETTERS 32 (3): Art. No. L03705 FEB 4 2005
Document Type: Article
Language: English
Cited References: 25 Times Cited: 2
Abstract: [1] In its motion through the Milky Way galaxy, the solar system encounters an average -density (greater than or equal to330 H atoms cm(-3)) giant molecular cloud (GMC) approximately every 10(8) years, a dense (similar to2 x 10(3) H atoms cm(-3)) GMC every similar to10(9) years and will inevitably encounter them in the future [Talbot and Newman, 1977]. However, there have been no studies linking such events with severe ( snowball) glaciations in Earth history. Here we show that dramatic climate change can be caused by interstellar dust accumulating in Earth's atmosphere during the solar system's immersion into a dense (similar to2 x 10(3) H atoms cm(-3)) GMC. The stratospheric dust layer from such interstellar particles could provide enough radiative forcing to trigger the runaway ice-albedo feedback that results in global snowball glaciations. We also demonstrate that more frequent collisions with less dense GMCs could cause moderate ice ages.