haqqmisra.net » publications

Sulfur Can’t Keep Mars Warm

Jacob — Mon, 28 Jun 2010 15:30:13 +0000

Satellites and rovers sent to Mars keep giving us compelling geologic evidence that liquid water flowed on the surface of the red planet in the distant past. Three billion years ago, when oceans may have existed on parts of Mars, the sun was about 30% fainter. Mars today is well below the freezing point of water, so any lakes or oceans would be frozen over. In the distant past, then, this problem is even more pronounced: how was Mars able to stay warm enough to sustain liquid water?

Many attempted resolutions have been proposed to this problem, but none has provided a complete solution for a warm, wet early Mars. In a recent paper published in Earth and Planetary Science Letters, on which I am a co-author, we argue that greenhouse warming by sulfur dioxide could not have kept early Mars warm enough. Sulfur dioxide has been suggested in the literature because it is an effective greenhouse gas, similar to carbon dioxide or methane. However, we show that atmospheric photochemistry with sulfur dioxide leads to the production of sulfate aerosols in the upper atmosphere that absorb incoming sunlight and cool the surface. Thus, sulfur dioxide may have caused net cooling on early Mars, rather than warming.

We’re still trying other mechanisms to explain a warm, wet early Mars. Most likely, it was some combination of processes, including several greenhouse gases and warming by clouds. A negative result for sulfur dioxide is not as exciting as a solution to the early Mars problem, but it’s still a small step forward.

Sky & Telescope article: Where have all the aliens gone?

Jacob — Wed, 20 Jan 2010 06:31:09 +0000

If intelligent life is common in the galaxy, then the fact that we have not yet observed any extraterrestrials raises the question: where are they? The upcoming March issue of Sky & Telescope magazine features an article written by myself and Seth Baum where we discuss how the conspicuous absence of extraterrestrials may relate to the problem of sustainable development on Earth.

Funny story, we were initially slated for the January issue (we even made the table of contents), but a printing error lost the last 10 pages which sadly included our article. Nevertheless, the Sky & Telescope staff are excellent people to work with and made a fast turnaround. Be sure to check out the March issue!

A Hazy View of the Early Earth

Jacob — Fri, 06 Feb 2009 21:08:45 +0000

My MS paper, “A Revised, Hazy Methane Greenhouse for the Archean Earth”, just appeared in the journal Astrobiology! You can view a PDF of the article on my research page.

We argue that the warm, ice-free climate of the early Earth (2.8 billion years ago) was maintained by a water vapor/carbon dioxide/methane/ethane atmospheric greenhouse effect that offset the ~20% reduction in solar luminosity from the faint young sun. Furthermore, a stabilizing feedback between life and the climate system may have resulted in a thin stratospheric organic haze that maintained above-freezing temperatures and shielded ultraviolet radiation. An excellent write-up of our work is available at The Planetologist.

I’ve given this talk several times over the past couple years, most recently on the Forum for Astrobiology Research (which should eventually be available as a podcast), and it feels good to finally see the paper come out.