Shortlist of Possible ET Addresses

An anonymous reader writes "Yahoo News is reporting that Astronomer Margaret Turnbull of the Carnegie Institution has released a 'top 10' list of potential inhabitable star systems. NASA is planning on using this top 10 list as the targets for their Terrestrial Planet Finder a 'system of two orbiting observatories scheduled for launch by 2020.'"

of particular concern is who is notified first

[wisebabo]

While the chances of hearing from alien worlds is depressing small ("Rare Earth"), still the thought that a few private individuals will know first should give us pause. If there is more information in the detected signal than "hello there", who knows what could be learned? Markets may move in a big way (here's how antigravity works, immortality, existence of god, a big black hole is headed your way, etc.).

Then again if that's the only way we're gonna get these projects funded, perhaps these philanthropists should be rewarded for their risk taking.

hmmm

[smash]

Apparently some systems were "tossed out" because they aren't stable enough (variable stars, strong gravity, etc).

Now, is it just me, or does the idea that life may well need some abnormal event to kick-start it in conflict with that very idea?

Perhaps include *some* of these systems?

smash.

Immigration?

[opencity]

"I've chosen five to advertise the very best places to move to if we had to, or to point the telescope at," she told the BBC.

An open call for science fiction references if there ever was one.

Her criteria include a temperate zone that can support copious amounts of liquid water. If we're moving, I agree. There are chemical reasons we think life would be predisposed toward water but there could be different biochemistries. Any biochemists out there feel free to disagree and/or expound.

This story is also a good test of the slashdot equivalent of Godwin's law. How long until the usual sectarian debates spring up (and I don't mean MS)

Recent Articles on the Origin of Life

[Quirk]

The Royal Society is holding a symposium on the origins of life...

Life on Earth 'unlikely to have emerged in volcanic springs' [royalsoc.ac.uk]

13 Feb 2006

"The latest findings of experiments to re-create the conditions under which life could emerge from chemical reactions suggest that volcanic springs and marine hydrothermal events are unlikely to have provided the right environment, a leading researcher from the United States will tell an international meeting tomorrow (14 February 2006) at the Royal Society, the UK national academy of science."

In the alternative Plos ran an interestin article titled Jump-Starting a Cellular World: Investigating the Origin of Life, from Soup to Networks [plosjournals.org] which touches on the front running theories on the origin of life.

Re:Terrestrial Planet Finder has been cancelled...

[helioquake]

Have you ever heard of things called "propaganda"?

And "cancellation" and "postpone indefinitely" mean different things. I think that TPF is listed as the latter (but correct me if I am wrong, of course!).

Re:of particular concern is who is notified first

[Toby The Economist]

> While the chances of hearing from alien worlds is depressing small ("Rare Earth"),
> still the thought that a few private individuals will know first should give us
> pause.

It seems to me this is a venture like any other. You put your money where your mouth is, you take a risk, and if it pays off, you get a reward. Smart investors look for low risk, high reward; this particular investment I think is high risk, high reward. Fair's fair and good luck to them!

Re:hmmm

[thedletterman]

I don't see anything wrong with their reasoning. Instable environments don't produce abnormal, life-forming events, they regularly produce events that are hostile to life. I saw a screening of a film last year at USF called The Privledged Planet [discovery.org]. Admittedly, it gratuitous in support of "purposeful design", but they did a great job of approaching what makes Earth so suitable for life using a myriad of fields. It may suggest life with a purpose, but it was strongly pro-science, and probably worth a watch, even if you are skeptic of the premise. Not only are some of the theories presented innovative, but the imagery and cinematography rival are reminiscent of an imax presentation.

Re:Immigration?

[cruachan]

"Any biochemists out there feel free to disagree and/or expound."

I'll take that one. In a liquid water environment it's difficult to see how you'd end up with a biochemistry that wasn't nucleic acid, protein, carbohydrate and fatty acid based. By observation life on earth seems to have explored just about every type of possible molecular structure that carbon/hydrogen/oxygen + other minor elements can produce and if there were some other useful biological molecule then it's difficult to imagine why it's not been 'discovered' and exploited already. That's not to say that the details won't differ - I'd have thought it virtual certain that a mix of different nucleic acids and amino acids would be used in different combinations with a different genetics etc etc, but I'd expect life to be grossly similar on similar planets, just differing radically in the details.

Outside that I'm very unconvinced by non-water or carbon based life. Silicon just doesn't form complex enough molecules so that's out. The next best bet seems to me to me ammonia based.

Re:Keeping it secret

[Anonymous Coward]

I think that in the event of finding E.T life, SETI just might, you know, tell some other people as well.

But only after the financers have placed their bets on the stock market.

And if the transmission contains suitable material filed a few patents. (Or does LGM tech constitute prior art?)

Re:Keeping it secret

[Monkeys!!!]

"But only after the financers have placed their bets on the stock market.

And if the transmission contains suitable material filed a few patents. (Or does LGM tech constitute prior art?)"

I would like to think that the contract the private investors sign to be involved states that all information gained from transmissions are public domain. Then again the project might be desperate enough for money that they would allow the investors to keep control of what they recieve.

Terrestrial planets maybe. Intelligent life not!

[bradbury]

It is unfortunate that Turnbull, the Carnegie Institution and NASA chose to affiliate themselves with the Search for Extraterrestrial *Intelligence*. TPF might be capable of locating "water worlds" but there is no experimental information with regard to what fraction of those might have no water or be entirely covered in water (water worlds). It seems obvious that planets like Venus and Mars do not support life or may have only supported it for a brief period (in large part because they are near the edges of the habitable zone). It is also difficult to envision how intelligent life, particularly intelligent life with robust technology (radio transmitters, integrated circuits, rockets, etc.) would evolve on planets entirely covered in water. So one needs to make careful distinctions between systems with dead planets, systems with only water covered planets (pure water worlds), systems with water worlds with primitive life (e.g. those before the Earth's current stage of development), systems with water worlds with intelligent life (our current stage) and those beyond our stage.

Lets do the math. Universe, ~13 billion years old. Earth, ~5 billion years old. Time to develop first sun-like stars perhaps 1 billion years. So there is a reasonable chance that there are (or were) Earth like planets up to 7 billion years older than Earth (at least around stars slightly smaller than the sun which age more slowly). There are some systems with younger Earths (*much* younger for those systems currently in the process of planetary formation). Lineweaver's group has worked on this and has concluded that ~70% of the Earth's in the galaxy are older than ours -- many of them by billions of years.

Based on this it is unlikely that either TPF or SETI (based on its current approaches) will discover "intelligent" life. The statistics dictate that you only have perhaps a 5000 (years) / 12,000,000,000 (years) chance (less than 1 in a million) of finding a planet which hosts "intelligent" life as we know it.

For those systems with terrestrial sized planets and those with water TPF is a reasonable effort -- it might manage to detect water and if lucky atmospheric composition that could hint at life. However pointing the SKA (or any other radiotelescopes) at the stars in the list provided are highly unlikely to be successful because they assume intelligent civilizations which are currently at (and remain at) our stage of development. (This changes the statistics to about 1 in a billion.)

The reasons for this are as follows... Whether you believe in steady state growth (Dyson's assumption in 1960), or exponential growth as "The Singularity [wikipedia.org]" concept proposes the bottom line is that it seems very unlikely that a civilization would actively choose to remain at our state of development (i.e. zero growth for millions or billions of years). If you choose the steady state model the time to develop to a Dyson Shell is measured in a few hundred to a few thousand years. If you choose the singularity model then the time to develop a Matrioshka Brain [aeiveos.com] (also here [wikipedia.org]) is measured in decades. Once either of those states is reached the star goes "dark". So the star list is useless (to either the TPF mission or SETI) for identifying locations of intelligent civilizations with capabilities even slightly beyond our own.

Robert Bradbury

Notes:
For the above calculations I chose 5000 years as the longevity of humans with a reasonable level of technology development. One could limit it to smaller time frames (~100 years for radio or 40-50 years for lasers or rockets). TPF has a much greater chance of being successful than radio or optical SETI because it is working with a much larger time window. Water world longevities range from 100 million to many billion years if they restrict themselves to sun-like (

Correction -- Two "Top 5" Lists, and more...

[SirBruce]

The submitter got it slightly wrong. First off, Margaret Turnbull's team came up with a list of 17,129 potentially habitable star systems in 2003, and the work she has done since has been to refine that list.

What she announced yesterday were TWO "Top 5" lists. The first list includes the top 5 recommendations for a SETI search:

beta CVn
HD 10307
HD 211415
18 Sco
51 Pegasus

The second list includes the top 5 recommendations for the TPF to examine for Earth-like planets:

epsilon Indi A
epsilon Eridani
omicron2 Eridani
alpha Centauri B
tau Ceti

Why the difference? Well, the second list is of much closer stars, and much more likely to have planets that TPF can find and image. The first list has stars that are a bit farther away, but are, generally speaking, more like our Sun.

And here's a useful link:

http://www.aaas.org/news/releases/2006/0218habitab le.shtml [aaas.org]

Bruce

Re:of particular concern is who is notified first

[instarx]

If there is more information in the detected signal than "hello there", who knows what could be learned? Markets may move in a big way (here's how antigravity works, immortality, existence of god, a big black hole is headed your way, etc.).

I think you are underestimating the effect that just the knowledge that there are other intelligences out there would have. The "Hello there" message would be quite enough to roil stock markets, cause riots, etc. Tens of people have been killed in riots over cartoons lately, what do you think would happen if three of the world's major religions had their basic beliefs challenged?

Frankly, if I knew that an announcement was going to be made that intelligent life had been discovered in another solar system, I'd be wishing for a remote mountain hideaway in the Southern hemisphere.