Superhabitable worlds

I just heard this story on NPR yesterday and the topic of superhabitable planets is superrelevant to our discussion of what life is and what conditions might exist where it is formed.

 

 “In their hunt for potentially habitable planets around distant stars, scientists have been so focused on finding Earth-like planets that they're ignoring the possibility that other kinds of planets might be even friendlier to life, a new report says.

So-called superhabitable worlds wouldn't necessarily look like Earth but would nonetheless have conditions that are more suitable for life to emerge and evolve, according to the article published this month in the journal Astrobiology.

"In my point of view, astronomers and biologists are biased," says , an astrophysicist at Canada's McMaster University who is the study's lead author. "These scientists look for planets that are Earth-like."

But it's possible that Earth is actually only marginally habitable by the standards of the universe, says Heller, who points out that our home may not represent a typical habitable world.

He and co-author of Weber State University in Utah have come up with a long list of traits that might make a planet "superhabitable."

The scientific journal article discussed on NPR is available here (just published!).

HellerRené and ArmstrongJohn. Superhabitable worlds.  Astrobiology. 2014. 14(1): 50-66.

Self-sustained Replication of an RNA Enzyme

Now I have to remember all the places in lecture I said I would post a link to the blog. Here's the first I remembered, a 2009 paper in Science

Self-sustained Replication of an RNA Enzyme

RNA enzymes have been made to undergo self-sustained replication in the absence of proteins, providing the basis for an artificial genetic system.

An RNA enzyme that catalyzes the RNA-templated joining of RNA was converted to a format whereby two enzymes catalyze each other’s synthesis from a total of four component substrates. These cross-replicating RNA enzymes were optimized so that they can undergo self-sustained exponential amplification at a constant temperature and in the absence of proteins or other biological materials. Amplification occurs with a doubling time of about one hour, and can be continued indefinitely. 

Late heavy bombardment update

New research reveals that the Archean era -- a formative time for early life from 3.8 billion years ago to 2.5 billion years ago -- experienced far more major asteroid impacts than had been previously thought, with a few impacts perhaps even rivaling those that produced the largest craters on the Moon, according to a paper recently published online in Nature.

They found that approximately 70 (and 4) dinosaur killer-sized or larger impacts hit the Earth (and Moon) over a span that lasted between 3.8 and 1.8 billion years ago.

The implication of such enormous impacts over the Archean era is unknown, but some are believed to have released nearly 500 times the blast energy of the Chicxulub impact. (aka the one that wiped out the dinosaurs)


"It will be interesting to see whether these mammoth events affected the evolution of early life on our planet or our biosphere in important ways," says Bottke. 

Quotes are from the ScienceDaily report and the original paper is here:
An Archaean heavy bombardment from a destabilized extension of the asteroid belt. Nature, 2012

What is life?

An article in this week's The Scientist takes a look at the old problem of just what exactly is life? Drawing on some recent papers they suggest that it is self reproduction with variation that is key.

The hypothetical primitive RNA replication process has a degree of sophistication that separates it from mere chemistry: it copies itself and allows copying mistakes, which themselves are copied in future generations. In other words, this is the process of self-reproduction with variations (as in Spiegelman’s system), not just organic synthesis. This is the very definition of life suggested by the developing theory of early molecular evolution. The same formula is derived by “word count” analysis, which yields the most frequently used words, of more than 100 known definitions of life. The recent discovery that both genes and genomes appear to have emerged originally as simple tandem repeats, with subsequent mutations increasing their complexity makes such definition even more attractive. One can view a genome as molecular habitat for emergence of “new life” in the form of expanding and mutating simple repeats. In that sense, and under the above minimalistic definition, life never stopped emerging, starting some 4 billion years ago with replicating RNA, and continuing to this day within the genomes of every living organism.

Sample size >>1

A few years ago we had not identified a single planet outside our solar system. Today the estimate is up to 100,000,000,000 (give or take a few). In fact the study of exoplanets is hot stuff at the moment with Nature papers generating headlines about exoplanets both yesterday and today.

Here's today's paper from Nature:
One or more bound planets per Milky Way star from microlensing observations
and one, of many, news reports - this one from the BBC: More planets than stars?

Yesterday's paper was about the recent discovery of several new planets that orbit multiple suns,
Transiting circumbinary planets Kepler-34 b and Kepler-35 b.
Was there a press report that didn't mention Tatooine? Real-Life Tatooine: Planets With Two Suns Found 

Start the quarter with a bang

I thought I was going to have to skip my traditional opening to the Winter blog because YouTube had taken this down but it's back. Also this is an opportunity to remind you that as we go through the course you can click on the labels at the bottom of the posts to review past postings. For example as well as my yearly version of this post the Abiogenesis label has a small, but interesting, collection of posts

For everyone who has ever wondered what it would be like when a 500km diameter asteroid crashes into the earth here's a simulation. Asteroids of this size would have impacted the earth during the late heavy bombardment I mentioned. If you go to YouTube to watch it you can click a little link to watch it in high def. (highly recommended). You might also want to wait until you can crank up the speakers. The perfect soundtrack to the end of the world.

Experiment Exploded ! ! !

Here's the link to the Miller-Urey experiment simulator I mentioned in class. Not only is this a fun little simulation but it is also a snapshot of how the internet looked 10 years ago with tiny videos in mpg format!

Still fun though. See how many goes it takes you to actually simulate the experiment correctly.

Thursday's wonder

Whoa. This is where stars are born. This is a new image of the North America Nebula from NASA's Spitzer Space Telescope. You can see the massive full size image here. Why is this important? - in all likelihood our Sun and its planets formed in a nebular cloud very much like this one.

Each little pinpoint speck of light in Spitzer's image is a young star at some particular point in its development., and haven't even become true stars yet—that only occurs when thermonuclear fusion kicks off in their cores. Others have begun their stardom, but are still sheathed in spherical cocoons of gas and dust, shells of material that will gradually grow puffy and vaporous from the inner star's light and heat, until they whisper away on stellar winds. Many of these points of light are ringed by thick accretion disks of material that formed from the angular momentum of their initial gravitational collapse. Sometimes parts of the disk get sucked too close to the star, and are shocked into plasma and spun away and out from the star's poles in powerful collimated jets that can sculpt and shape the surrounding gas and dust into abstract whorls and tendrils. And, in the background, almost unnoticed against all the stellar fireworks, in all probability planets are slowly and surely forming. Perhaps, on a few them, the seeds of life are already being sown by comets and meteorites, the infalling detritus of star formation delivering water and complex chemical compounds brewed in the stellar clouds. Some are still undergoing their initial gravitational collapse.


I tried to find a website that could explain where the  North America Nebula was in easy to understand terms and found just what I was looking for here. Unfortunately I then kept zooming out until my head exploded.

Extreme Planet Makeover

Well that's very topical. In a post to BoingBoing today is a link to NASA's 'Extreme Planet Makeover' website where you can design your own planet and then assess it's chances for life. You set the parameters for the planet and then click on the planet top find it assessed into one of a number of categories. As the BoingBoing post points out though:

If it seems like there's only a few, very limited ways to "win" this game ... well, that's kind of the point. The planet-builder is based on what we know about what it takes to produce life as we know it. And that list of requirements and contradictions really narrows your options. Ultimately, this site should make it clear why finding a "Goldilocks" planet is such a chore, and why everybody is so prone to get excited about the possibility that "life as we know it" isn't the same thing as "life".

It all starts/ends here

Posting the same thing twice is a repeat. Posting it three times is a tradition.

At various points this quarter we'll be talking about the origin of life, the early history of the earth and the importance of asteroid impacts.

For everyone who has ever wondered what it would be like when a 500km diameter asteroid crashes into the earth. If you go to YouTube to watch it you can click a little link to watch it in high def. (highly recommended). You might also want to wait until you can crank up the speakers. The perfect soundtrack to the end of the world. Or the beginning...

Panspermia

Panspermia is the idea that life on earth was 'seeded' by the arrival of organisms or compounds from space. Not necessarily little green men with a sinister plan, but maybe primitive microbes that then evolved into all life on earth. An interesting idea that is usually rarely mentioned in biology courses because, for me at least, the more interesting question is could life have once spontaneously arisen on earth? If so, under what conditions and how do these conditions relate to what we know about the early earth?

However if you want to read more about panspermia there are some fanatics on the web (just google it) or you can read this 2005 Scientific American paper - Did Life Come From Another World? for a more balanced view.

Start with a bang

Okay, I'm allowed to have the odd repeat. I think I shall make it a tradition to start this course with a bang.

We didn't actually get onto abiogenesis and the very early history of the earth today (don't worry we'll get to it later). However I don't think I'll let that stop me posting this clip from the Discovery Channel. For everyone who has ever wondered what it would be like when a 500km diameter asteroid crashes into the earth. If you go to YouTube to watch it you can click a little link to watch it in high def. (highly recommended). You might also want to wait until you can crank up the speakers. The perfect soundtrack to the end of the world.

Controversy Over World’s Oldest Traces Of Life

ScienceDaily (Feb. 28, 2009) —
The argument over whether an outcrop of rock in South West Greenland contains the earliest known traces of life on Earth has been reignited, in a study published in the Journal of the Geological Society. The research, led by Martin J. Whitehouse at the Swedish Museum of Natural History, argues that the controversial rocks "cannot host evidence of Earth’s oldest life," reopening the debate over where the oldest traces of life are located.

Life on Mars?

The definitive discovery in Mars’ atmosphere of methane — often, but not always, a compound hinting at life — introduces the possibility of underground organisms.

A paper from yesterdays edition of Science raises some intriguing possibilities that underground 'microbes' may be producing methane on Mars. Or maybe it's just a natural phenomenon:

About 0.6 kilograms of methane emerge each second in the summer, Mumma said, which is comparable to the emissions from a natural oil seep near Santa Barbara, California.

Thirty six years later and we still don't know if there is Life on Mars.

The year of Darwin

If Charles Darwin had had a laptop, he probably would have been a blogger--so eager was his desire to disseminate and discuss his ideas with the world.

I think I already mentioned here somewhere that 2009 will see BOTH the 150th anniversary of the Origin of Species and the 200th anniversary of Darwin's birth. The journal Science has a page that collects together news features, scientific reviews and other special content. There are already some interesting things there and I believe they are planning a monthly series of essays celebrating Darwin so it will be worth checking back later in the year.

Three days ago, the second issue of Science in the year contains a very important paper on abiogenesis, 'Self-Sustained Replication of an RNA Enzyme'. We will talk abou this later in the course but although an RNA 'world' has been postulated as a precursor to our DNA world no-one, to date, has shown that RNA replication could be self propagating (ie RNA acting as the enzyme that can replicate itself without the help of other molecules or cell components). There's a nice writeup of the work at ScienceDaily.

This is pretty big news. NPR had a brief interview with the lead author on All Things Considered today which you can listen to here.

Start the quarter with a bang

We didn't actually get onto abiogenesis and the very early history of the earth yesterday (don't worry we'll get to it later). However I don't think I'll let that stop me posting this clip from the Discovery Channel. For everyone who has ever wondered what it would be like when a 500km diameter asteroid crashes into the earth. If you go to YouTube to watch it you can click a little link to watch it in high def.

Protobionts

Okay, we are off to a great start here, almost half the class has signed up already and the posting has begun.
Here is a link to a really nice website at Cornell for an Introductory Biology class. On the linked page there is a nice description of protobionts and coacervates, and, on the left, some useful links to further origin of life information. Coacervates are one type of protobiont.

Mica

Okay, I finally get around to eating my lunch so I open this week's edition of 93106 - the weekly faculty and staff newspaper for UCSB - and what is right there on the front page?

'Mica Layers may have hosted life's first cells says new theory'

Research on the origin of life going on right here on campus.