» subscribe newsletter   » archived lectures




David Catling
University of Bristol




The Earth's atmosphere
Although a terrestrial planet's atmosphere barely extends above its surface, this is the ocean of gas in which life evolves.








July 10, 2006

Part VIII: Astrobiology

Evolution of the Early Atmospheres
of Venus, Earth and Mars
David Catling, University of Bristol
23 min. (slideshow requires QCShow Player)
Audio only (mp3 format)
View as a webpage (quicktime, real player) (notes)

Fire, air, water, earth, we assert, originate from one another, and each of them exists potentially in each, as all things do that can be resolved into a common and ultimate substrate.
— Aristotle, 384 BC – 322 BC

In the current movie, An Inconvenient Truth, Al Gore quotes Carl Sagan, saying that the Earth's atmosphere is approximately as thick proportionally as the layer of varnish is on a large globe. In reality, it's thicker than that, but not by much.

If water is the sine qua non of life, then an atmosphere of a minimum surface pressure is the sine qua non of water. Without sufficient pressure and heat, liquid water can't exist on a planet's surface.

Planetary conditions foster life, and in turn, life changes the geological evolution of the planet. Oxygen atmospheres overlaying oceans of water is not an equilibrial condition and they should not be expected a priori in any simple chemical thermodynamical model.

Whether life exists on other planets remains one of the great unanswered questions. Recent research argues that an atmosphere rich in oxygen is the most feasible source of energy for complex life to exist anywhere in the universe, thereby limiting the number of places life may exist.

Since David Catling gave this talk, Catling, now at Bristol University, along with colleagues at the University of Washington and NASA, have recently contended that significant oxygen in the air and oceans is essential for the evolution of multicellular organisms, and that on Earth the time required for oxygen levels to reach a point where animals could evolve was almost four billion years.

Because four billion years is almost half the anticipated life-time of our sun, life on other planets orbiting short-lived suns may not have had sufficient time to evolve into complex forms. This is because levels of oxygen will not have had time to develop sufficiently to support complex life, before the sun dies. This may well be a major limiting factor for the evolution of life on otherwise potentially habitable planets.

Catling comments: "Earth's surface is stunningly different from that of its apparently lifeless neighbours, Venus and Mars. But when our planet first formed its surface must also have been devoid of life. How the complex world around us developed from lifeless beginnings is a great challenge that involves many scientific disciplines such as geology, atmospheric science, and biology".

In this lecture, Catling outlines the evolution of the atmospheres of Venus, Earth and Mars. Two factors, as you will see, significantly predetermine the evolution of those atmospheres: planetary position and size.

Because this talk was originally presented at a conference on early Mars, Catling ends the lecture emphasizing the nature of the evolution of the current Martian atmosphere.

— Wirt Atmar


About the Speaker

David Catling is one of England's first Professors of Astrobiology and has recently returned from the USA to take up a post at the University of Bristol. He took up a prestigious 'Marie Curie Chair', an EU-funded position designed to help reverse the brain drain, particularly to the USA, and to encourage leading academics to return to and work in Europe. These posts aim to attract world-class researchers. Professor Catling is an internationally recognised researcher in planetary sciences and atmospheric evolution.

Professor Catling received his doctorate from Oxford, but he has been working in the USA for the past decade: six years as a NASA scientist, followed by four years at the University of Washington in Seattle. Professor Catling is now based in the Department of Earth Sciences at the University of Bristol.

As well as his research into the surface and climate of Mars, Professor Catling aims to produce a more quantitative understanding of how the Earth's atmosphere originated and evolved.

Professor Catling is also part of the science team for NASA's Phoenix Lander, which recently got the go-ahead to put a long-armed lander on Mars in 2007. A robotic arm on the lander will dig a meter into the soil to examine its chemistry. A key objective is to establish whether Mars ever had an environment conducive to more simple life.


Subscribe to the Weekly Notice

If you wish to receive a weekly notice of the current lecture, please send a blank email to:

lectures@aics-research.com

Privacy Policy: Your email address will be shared with no one nor used for any purpose other than sending you the weekly lecture notice.

These Lectures are Sponsored by
AICS Research, Inc.

You can easily create lectures of equal quality yourself.

The internet has obvious promise for the dissemination of instructional material over very large distances and into remote corners of the world. To that end, AICS Research has created two products, QCShow, a freely-downloadable player, and QCShow Author, an inexpensive content authoring tool that produces FM-quality sound and full-screen HDTV-quality slideshows at very low bandwidths.

As an adjunct to that development process, for the past 30 months AICS Research has been recording the highest quality conferences in cosmology, astronomy, planetology, geology, astrobiology, ecology, behavior and evolutionary biology so that these presentations may be viewed by anyone anywhere in the world.

The QCShow Player was designed for both individual viewer and for the classroom, so that you may "team teach" with the lectures. Indeed, you may run the lecture through a classroom projector and your room's sound system and very closely recreate the lecture as it was first presented live, but now with the capacity to instantly pause the speaker and interpose your own commentary wherever you wish.

QCShow Author was similiarly designed to be as simple a mechanism as possible, allowing a single lecturer to create productions equal to the very best of educational television, but very quickly, and at astoundingly low costs.


Copyright Notice: AICS Research asserts no copyright over any of the lectures presented in this series. Whatever copyrights exist, they reside with the original authors. You have been given permission to save these lectures on your local machines if you wish, so long as they are not modified in any manner.