I found a good review of all the recent literature on how things from space have effected Earth over the millennia.
From arXiv:
The evidence for and against astronomical impacts on climate change and mass extinctions: A review
The author covers the the geological record, and then discusses the findings on Solar System objects, cosmic rays, supernovae, GRBs, Solar variability, Milky Way plane crossings, spiral arm crossings, etc.
There's an emphasis on studies discussing periodicity, and the author concludes that there is little evidence to suggest either long-term periodicity of events on Earth, or that periodic Galactic events (e.g spiral arm crossings) have much influence here.
As far as I can tell, the author did not use the modified Milky Way structure that was recently revealed, but that was covered by Fraser's thread
here, and the referenced study, also on arXiv
here.
The abstract:
Quote:
Numerous studies over the past 30 years have suggested there is a causal connection between the motion of the Sun through the Galaxy and terrestrial mass extinctions or climate change. Proposed mechanisms include comet impacts (via perturbation of the Oort cloud), cosmic rays and supernovae, the effects of which are modulated by the passage of the Sun through the Galactic midplane or spiral arms. Supposed periodicities in the fossil record, impact cratering dates or climate proxies over the Phanerozoic (past 545 Myr) are frequently cited as evidence in support of these hypotheses. This remains a controversial subject, with many refutations and replies having been published.
Here I review both the mechanisms and the evidence for and against the relevance of astronomical phenomena to climate change and evolution. This necessarily includes a critical assessment of time series analysis techniques and hypothesis testing. Some of the studies have suffered from flaws in methodology, in particular drawing incorrect conclusions based on ruling out a null hypothesis.
I conclude that there is little evidence for intrinsic periodicities in biodiversity, impact cratering or climate on timescales of tens to hundreds of Myr. Although this does not rule out the mechanisms, the numerous assumptions and uncertainties involved in the interpretation of the geological data and in particular in the astronomical mechanisms, suggest that Galactic midplane and spiral arm crossings have little impact on biological or climate variation above background level.
Non-periodic impacts and terrestrial mechanisms (volcanism, plate tectonics, sea level changes), possibly occurring simultaneously, remain likely causes of many environmental catastrophes. Internal dynamics of the biosphere may also play a role. In contrast, there is little evidence supporting the idea that cosmic rays have a significant influence on climate through cloud formation. It seems likely that more than one mechanism has contributed to biodiversity variations over the past half Gyr.
|
27-June-2009, 08:16 PM
Astronomical Phenomena And Mass Extinctions: A Review
Similar Threads
Linear Mode
