Once more on the search for exoplanets, and Alpha Centauri

Excuse me for the absence of regular science posts, but my brain has turned to mush from writing fantasy. Isn’t it easy when you’re allowed to make everything up and as long as it makes sense, no one cares about accuracy? But, yes, I will return to where I left my characters in the Jupiter system, or in a space station orbiting the fictional gas giant Sarasvati, in the not-too-distant future.

This morning I came across this very interesting article on the Centauri Dreams website. By the way, Centauri Dreams, the website of the Tau Zero Foundation, is a very rich source for writers of realistic SF, especially in relation to planetary exploration and interstellar travel.

The article summarises results and speculation arising from new planets discovered by the European Southern Observatory’s HARPS spectrograph, which provides the most accurate Radial Velocity measurements we currently have (see an earlier post on how planets are discovered). Because of its increased sensitivity, HARPS can detect smaller planets. The smallest planet found at this point in time is a mere 1.5 times Earth’s mass. One of the, perhaps expected, outcomes of the spectrograph’s bevy of newly found low-mass planets (super-Earths or near Earth-mass) is that there are many of these smaller planets, a lot more than there are very large planets, and that the previous bias was merely a product of larger planets being easier to detect. The galaxy is swarming with smallish rocky planets. It is quite likely that some will be found inside the habitable zone.

We may already have found some of these planets. Much was made last year of the ‘discovery’ of Gliese 581g, supposedly in the habitable zone of an M class star. However, further analysis has so far failed to confirm the existence of this planet. But the star has two other planets which orbit at the edge of the habitable zone, and out of these, Gliese581d looks the most promising. The width of the habitable zone is not absolute, but varies with the planet’s albedo (basically, how much light it reflects) and composition and (if any) atmosphere composition (see another post on that here). So a newly discovered planet, HD85512b, at 3.6 Earth masses, may also fit the bill. It is a little close to its K class parent star, but could harbour liquid water on its surface if certain conditions of composition and atmosphere are met (see original paper by Kaltenegger et al. here).

Using the HARPS spectrograph, another group of researchers report on the search for planets orbiting sun-like stars within 40 light years from our solar system. (original paper by Pepe et al here). This work has resulted in a the discovery of a number of planets, again, most in the smaller size category. One of the main targets for the hunt is Alpha Centauri B, but there are some problems, one of the main ones being that it is part of a triple star system, and that any model the describes the wobble of the star that is caused by an orbiting planet must take into account that there are two other stars in the system, and as you could understand that is tricky business.

Image depicting an exoplanet system snarfed from NASA JPL

Is there other life in the universe?

Let’s start with the solar system. People very much want there to be life in the solar system. We’d like to think that the presence of life on Earth is not unique, and that life in some form also exists, or has existed, in other places. But where would this life have come from?

There are two main theories about the emergence of life from the soup of hydrogen, oxygen, carbon and nitrogen in primordial soup. One, the geocentric model, is that life emerged on Earth and is therefore unique to Earth. The other theory takes a more holistic view in that Earth is not central to the universe. We are uncommon, but not special or precious.

Panspermia has life originate in microbial form elsewhere in the universe and being spread through comets. While we have no definitive proof for either theory, there are some pointers. Firstly, the elements for life exist everywhere in the universe. In limited, but still reasonably numerous, places, temperatures are right for liquid water. Life on Earth evolved in liquid water. Secondly, certain bacteria are known to survive exposure to space for extended periods. Certain bacteria can lie dormant for many, many years. It is feasible to assume that these bacteria would not have developed these abilities unless there was a need for them.

How could we find out?

Sample return missions to places of interest are expensive. They will eventually be necessary, but there are other things we can do to pinpoint things to look for when eventually we send such missions.

We can look at comets. If comets carried the first microbes to Earth, they would also have carried them to other bodies. There is no reason to believe that if comets carried microbes millions of years ago, they have suddenly stopped doing so.

We can look at how and where organisms have survived in environments on Earth that are too hostile for most other life. This explains the interest in extremophiles, organisms that thrive in such places. It is with this in mind that scientists look for life in hydrothermal vents in the dark depths of the oceans, where the water welling up is extremely hot, where it is extremely dark and there is little oxygen to be had. It is for this reason that scientists look for adapted life in Antarctica, or in environments that are too poisonous for ‘normal’ life to exist.

We can look at bits of other celestial bodies that have found their way to Earth

That said, in recent months, we’ve seen a number of disappointing reports. First, there was the big kerfuffle over the discovery of bacteria that can substitute arsenic for phosphorus. While the research was officially announced, a big hoo-hah soon broke out over the validity of the results.

Then, last month, there was a report that fossil bacteria had been found in meteorites that are of Martian origin. Again, a big bunfight broke out, this time including claims against the reputation of the magazine in which the paper had been published.

This is starting to sound very much like the boy who cried ‘wolf’ too often, or maybe too soon, when the wolf was in fact the neighbour’s dog. It’s sad because as described above, a discovery would probably fall along those lines. This hyped-up (pseudo) news desensitises people to the real possibilities.

Meanwhile, a good number of well-informed scientists express the quiet opinion that we will ‘probably’ find evidence of microbial life elsewhere in the solar system. Candidates for such finds would be fossil life on Mars, extant life in the seas of Europa and possibly methane-based life on Titan. They also think that any such life is likely to be primitive, possibly no more evolved than bacteria. No one thinks we’ll be meeting little green men any time soon.

What were you doing?

Inspired by a couple of blog posts at Tor.com and some discussion on Facebook, I thought I’d post my impressions on that day people first walked on the Moon.

Like the author Jo Walton, who has posted on the blog, I was four, and I remember the day vividly. It was sunny. We visited my grandparents, who had tv, and the tv was on, my grandfather glued to it. We didn’t have tv at home, and there was a meticulously enforced rule in our family that when visitors came, the tv was switched off. So wow, my grandpa was watching tv. And everyone sat down in the living room, despite the nice weather outside, and we all had to watch, and be quiet, because we Absolutely Had To See This. Because people were landing on the Moon. Ba humbug. People had been talking about the Moon, and going there, all my life. What was so special about that?

I was, of course, a child of the space age. What was very special to my parents and grandparents wasn’t to me, just like my kids now regard computers and mobile phones as extensions of their life, so was for me the feeling that people could do anything just natural. Cure cancer? Shrug. Eventually we’ll get to the bottom of it. Nanotechnology? Shrug. It will be useful some day. Genetic engineering? Shrug. Why not? Sending people to Mars? Of course. The universe is your oyster.

And then something happened.

Somehow, cutting-edge technology for the benefit of science, for the benefit of society in general, has become irrelevant. We, the me-generation, demand immediate return for investment in science. We rather see a better mobile phone than people on Mars. We are inclined to vote with our hip pockets. Long-term goals have fallen by the wayside. The space program has not been the only victim of this trend. Few countries maintain visionary programs for public transport. Most cities limp and fix outdated infrastructure rather than spend money on updates that will last for at least 25 years and are based on growth. Industry is expected to foot the bill for scientific research. Everything that encompasses ‘the public good’ has been steadily and stealthily eroded.

In this climate, it’s not viable to suggest spending large amounts on space exploration without that one thing people want: clearly defined goals. The characteristic of pure science is often that it does not have clear goals, but that afterwards, there are unexpected benefits. It would love to see continued space exploration, but I think that will only happen when the urgency returns. Another race between nations, maybe, or some event on Earth that jolts us into action. When that happens, will there be another Age of Wonder?