[X] My Assistant

[Guest_AlexBlackwell_*]

The latest issue of Astrobiology (Volume 6, Number 1, January 2006) is now online.

[Guest_RGClark_*]

The latest issue of Astrobiology (Volume 6, Number 1, January 2006) is now online.

Thanks for that. It includes the announcement of the AbSciCon astrobiology conference in Washington D.C. coming up next week. I hadn't been aware of that. I might actually be able to make that one.

AbSciCon 2006: Agenda and Events.
http://abscicon2006.arc.nasa.gov/agenda-session-all.php

- Bob Clark

[Guest_AlexBlackwell_*]

Thanks for that. It includes the announcement of the AbSciCon astrobiology conference in Washington D.C. coming up next week. I hadn't been aware of that.

You're welcome, Bob, though I have to issue an admonishment since you didn't read my prior post on AbSciCon 2006.

[Guest_AlexBlackwell_*]

The latest issue of Astrobiology (Volume 6, Number 1, January 2006) is now online.

I made an error (actually an assumption) but the correct designation of the issue is Astrobiology (Volume 6, Number 1, February 2006). I edited the topic title to reflect this.

BTW, I just noticed a couple of things. The PDFs that were online when I first posted this were galley proofs. These have been replaced by final versions; indeed, there are now 18 PDFs for this issue instead of 19 as before. Also, I noted the publishers are offering free access to the AbSciCon 2006 abstracts. I know this is probably moot (not to mention slightly irritating to Astrobiology subscribers like me) since the abstracts are already freely available on the conference website.

[Guest_AlexBlackwell_*]

Here's a EurekAlert release today pertaining to the Fisk et al. paper: Mars meteorite similar to bacteria-etched earth rocks.

[Guest_RGClark_*]

Here's a EurekAlert release today pertaining to the Fisk et al. paper: Mars meteorite similar to bacteria-etched earth rocks.

Thanks for that. A very interesting report.

Bob

[ljk4-1]

UGA researchers propose new hypothesis on the evolution of hot springs microorganisms

Athens, Ga. – Since their discovery in the late 1970s, microorganisms known as archaea have fascinated scientists with their ability to thrive where no other life can – in conditions that are extremely hot, acidic or salty.

In the 1990s, however, scientists discovered that archaea occur widely in more mundane, low-temperature environments such as oceans and lakes. Now, researchers from the University of Georgia and Harvard University find evidence that these low-temperature archaea might have evolved from a moderate-temperature environment rather than from their high-temperature counterparts – as most scientists had believed. The results appear in the June 2006 issue of the journal Applied and Environmental Microbiology.

“Archaea represent one of the three domains of life on Earth,” said Chuanlun Zhang, lead author of the study and associate professor of marine sciences at UGA. “Understanding their evolution may shed light on how all life forms evolve and interact with the environment through geological history.”

Full article here:

http://www.uga.edu/news/artman/publish/060...otSprings.shtml

[Guest_DonPMitchell_*]

I think there is a difference between life adapting to harsh conditions and life forming in those conditions. Once complex organisms are well established, they have the genetic mechanisms to evolve into all sorts of forms, but that doesn't mean life would ever appear on a planet of boiling water.

On another note, have people looked at Carl Sagan's papers on life in the clouds of Venus? The concept has been "invented" anew by a couple scientists recently. Again though, there is the problem of formation vs. adaption. I don't believe for a second that there is life on Venus.

[Guest_BruceMoomaw_*]

Exactly this reasoning has been applied as an alternative explanation for why the most genetically primitve organisms remaining on Earth seem to be hyperthermophiles: when life was first evolving on Earth, the planet (which was usually rather cold, due to the dim early Sun) was still getting clouted every few tens of millions of years by really giant impactors capable of boiling most or all of the entire ocean into steam -- so that, even if life first evolved during the period between two such impacts, the only microbes that could surive such a catastrophe and carry on to continue evolving were the hyperthermophiles that existed at the time of the impact. This is now referred to as "the high-temperature bottleneck" for early terrestrial life.

It's conceivable that a chemical analog of this bottleneck may have existed for Martian life. That is, Martian life, if it exists, probably evolved in a neutral or moderately alkaline solution during the Noachian Era (since what little we know about prebiotic evolution suggests that it has serious trouble starting up in a highly acid environment). But after the Hesperian Era started and water was only capable of existing in liquid form on Mars' surface if it was mixed with substantial amounts of sulfuric acid, those microbes which had already evolved an ability to survive in highly acidic environments might still be able to carry on during that era. So looking for fossils in Hesperian acid-created sedimentary deposits like Meridiani may not be a complete waste of time, although the Noachian phyllosilicates discovered by Mars Express still seem to be the best targets.

[ljk4-1]

I don't know about any life on Venus now, but what about in
the early days when it was apparently a bit more environmentally
friendly?

http://www.newscientist.com/article.ns?id=dn2843

http://www.funkyscience.net/ch6.html

[Guest_DonPMitchell_*]

I just don't buy it. Nothing can be alive on Venus. If you dropped an organism into the clouds, atmospheric circulation woudl carry it down to be incinerated in the depths. These press releases about life on Venus are just publicity stunts. You would never hear the top scientists like Esposito or Head talking about junk like that. When Sagan was discussing the idea in the 1960s, much less was known about the actual conditions on Venus. It was still thought to have water-dropplet clouds and a much less dense atmosphere.

[ljk4-1]

I just don't buy it. Nothing can be alive on Venus. If you dropped an organism into the clouds, atmospheric circulation woudl carry it down to be incinerated in the depths. These press releases about life on Venus are just publicity stunts. You would never hear the top scientists like Esposito or Head talking about junk like that. When Sagan was discussing the idea in the 1960s, much less was known about the actual conditions on Venus. It was still thought to have water-dropplet clouds and a much less dense atmosphere.

Sagan promoted the idea of seeding Venus' clouds with algae from Earth
to introduce oxygen to the planet's atmosphere and start a terraforming
process. He wrote about it in a 1961 issue of Science magazine.

http://www.reference.com/browse/wiki/Terraforming

To reiterate, I agree that life on Venus now is quite problematic (but imagine
something that could survive in those conditions), but what about the two
billion or so years *before* things became overheated?

There was a recent discussion on this forum about Venus actually having
a longer period of time when conditions on it were good for life than Mars,
including oceans. The link is here:

http://www.unmannedspaceflight.com/index.p...indpost&p=53851

I wonder if it would be possible to find fossils? Or maybe something balloon-like
survived in the kinder, gentler regions of the upper atmosphere. If nothing else,
this just shows how much we still need to learn about this world.

A recent news item regarding Venus life and the possibility of contamination
from either there or Earth:

http://www.space.com/scienceastronomy/060221_venus_life.html

[ljk4-1]

The Evolutionary Biology Lecture of the Week for June 5, 2006 is now available
at:

http://aics-research.com/lotw/

The talks center primarily around evolutionary biology, in all of its aspects:
cosmology, astronomy, planetology, geology, astrobiology, ecology, ethology,
biogeography, phylogenetics and evolutionary biology itself, and are presented
at a professional level, that of one scientist talking to another. All of the
talks were recorded live at conferences.

This is the third lecture in a summer-long series on the new science of
astrobiology.

=====================================

June 5, 2006

Part III: Astrobiology

Taking the Galactic Planetary Survey

Gregory Laughlin, University of California, Santa Cruz

35 min.

"There are two distinct possibilities: either we are alone in the Universe,
or we are not. Both are equally terrifying."

— Arthur C. Clarke

The knock against astrobiology has remained the same for forty years now:
astrobiology is an area of study without a known subject. George Gaylord
Simpson famously wrote in an issue of Science (v.143, p.769) in 1964: "this
'science' has yet to demonstrate that its subject matter exists!"

Yet even should the discovery of a second, independent genesis of life
elsewhere in the universe remains decades away, astrobiology will nonetheless
profoundly change of our views of the evolution of life on Earth, in the
absence of that singular discovery. Geology was the science that informed and
transformed evolutionary thought during Darwin's time. Comparative planetology,
although it is a new field of inquiry, will do the same during ours.

Speculating on the evolution of life in the universe has always been a risky
business, and one not always highly regarded. Two hundred and fifty years ago,
when the first thoughts that the formation of the planets must have occurred by
secular (natural) means in the two competing cosmogenies of Buffon and Laplace,
rather than as part of a supernatural command, the ideas were met with at best
only tepid enthusiasm.

Life, up until recently, has always been a property unique to the planet Earth.
It really hasn't been considered in any other context. But we are now beginning
an extraordinary new voyage of discovery: we are beginning to take a galactic
survery of planets, at least in our very small region of the Milky Way. Because
of this, we are beginning to get a sense of the diversity of planetary systems
possible.

[ljk4-1]

Astrophysics, abstract
astro-ph/0606117

From: Masahiro Ikoma [view email]

Date: Tue, 6 Jun 2006 13:30:16 GMT (970kb)

Constraints on the mass of a habitable planet with water of nebular origin

Authors: Masahiro Ikoma, Hidenori Genda

Comments: 25 pages, 8 figures, to appear in the 01 September 2006 issue of ApJ

From an astrobiological point of view, special attention has been paid to the probability of habitable planets in extrasolar systems. The purpose of this study is to constrain a possible range of the mass of a terrestrial planet that can get water. We focus on the process of water production through oxidation of the atmospheric hydrogen--the nebular gas having been attracted gravitationally--by oxide available at the planetary surface. For the water production to work well on a planet, a sufficient amount of hydrogen and enough high temperature to melt the planetary surface are needed. We have simulated the structure of the atmosphere that connects with the protoplanetary nebula for wide ranges of heat flux, opacity, and density of the nebular gas. We have found both requirements are fulfilled for an Earth-mass planet for wide ranges of the parameters. We have also found the surface temperature of planets of <= 0.3 Earth masses is lower than the melting temperature of silicate (~ 1500K). On the other hand, a planet of more than several Earth masses becomes a gas giant planet through runaway accretion of the nebular gas.

http://arxiv.org/abs/astro-ph/0606117

[ljk4-1]

Evolution Takes A Hot Bath As Archaea Migrate

Athens GA (SPX) Jun 14, 2006

Since their discovery in the late 1970s, microorganisms known as archaea have fascinated scientists with their ability to thrive where no other life can - in conditions that are extremely hot, acidic or salty.

http://www.terradaily.com/reports/Evolutio...ea_Migrate.html


Parallel Evolution Found To Exist At Protein Level

by Staff Writers

Ann Arbor MI (SPX) Jun 14, 2006

Wings, spines, saber-like teeth-nature and the fossil record abound with examples of structures so useful they've evolved independently in a variety of animals. But scientists have debated whether examples of so-called adaptive, parallel evolution also can be found at the level of genes and proteins.

http://www.terradaily.com/reports/Parallel...tein_Level.html