August 28, 2006
Part XV: Astrobiology
Life and Death on Ice-Covered Worlds
University of California, Berkeley
24 min. (slideshow requires QCShow Player)
Audio only (mp3 format)
View as a webpage (quicktime, real player) (notes)
Three feet of ice does not result from one day of cold weather.
— Chinese proverb
The notion that the sciences of paleontology and astrobiology should be somehow linked seems quite jarring at first, but it only takes a moment's thought to see the logic in the connection.
Water is the sine qua non of life. Where liquid water disappears, the life we know similarly disappears. Although water is now rare on the inner planets of our solar system, it wasn't when the system was young. Mars and Venus have since lost their oceans, and the Earth is destined to do so as well. But there are places where water should persist for as long as the Sun exists.
In our search for life in the solar system, we're certainly going to look for the signs of ancient life in the former ocean basins of the inner planets, and thus paleontology is likely to become a key component of astrobiology, but there are other bodies in the solar system that appear to have large extant oceans of water, such as the icy moons of Jupiter and Saturn, albeit covered by kilometers of ice.
Earth, both now and in the past, has created an analog for these icy worlds. The idea of "Snowball Earth" proposes an Earth so cold that its oceans froze over completely, with only interior planetary heat allowing liquid water to persist below the ice. Two of these Snowball Earth episodes are apparent in the geological record, and both are coincident with significant, sudden increases in oxygen in the Earth's atmosphere, as explained by David Catling in an earlier lecture.
In this talk, Jere Lipps argues that ice-covered worlds are no barrier to life.
These worlds provide the three things life requires: the chemicals of life, the energy to drive it, and the habitats to support it. But death would also occur on these worlds, resulting in the potential preservation of life forms and products as fossils that may tell a story of the origin and evolution of life there, thus the necessity of a paleontological approach.
On Earth’s current and past icy worlds, life abounds. It lives in close association with ice-shelves and sea ice in Antarctica and the Arctic. Here life lives easily in a wide variety of sub-ice, inter-ice, and surficial ice habitats. Earth’s fossil record shows that life similarly endured the Neoproterozoic Snowball Earth, when the planet was covered entirely or substantially by ice. Life seems to have no problem with ice, so long as liquid water exists below it.
— Wirt Atmar
About the Speaker
Jere Lipps is Professor of Integrative Biology at the University of California (Berkeley) and Curator of Paleontology at the UC (Berkeley) Museum of Paleontology.
Aside from being past director of the UC Museum of Paleontology he is also a past president of the Paleontological Society. His research concerns the evolutionary biology and ecology of marine organisms, protists in particular. This involves studies of modern species and of particular problems in the fossil record. Presently, he is participating in studies concerning the biology and molecular phylogeny of coral reefs (Papua New Guinea, Enewetak Atoll, French Polynesia) and California foraminifera with the aim of better understanding the fossil record of these forms.
Paleobiologic projects include the evolution of the earliest shelled protists in the Precambrian and Cambrian and the biologic constraints on mass extinctions and radiations. These projects are mostly field oriented utilizing SCUBA in the modern studies and extended geologic work in the paleobiologic studies.
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