“Take Me To Kepler!”: The Exobiology of HZ Worlds

Drafted: 27 June; Revised: 29 June 2014

The search for exoplanets continues...
The search for exoplanets continues…

“Earth size planets  can and do exist in the HZ ‘s of other stars” – Doud Hudgins, Exoplanet Exploration Program.

Following on from the theme of last week’s Post, the oft-discussed topic of finding habitable worlds in the solar system is never far away. As technology advances, and astronomy becomes a more vital discipline, then the search for such worlds – and their possible inhabitants – gathers even greater pace, with a recent (March 2014) news story excitedly reporting the discovery of exoplanets “by the bus load,” with 1,692 confirmed and 3,845 suspect candidates, bringing the total to over 5,500.

 Incredible, when you consider that the first exoplanet, orbiting within its HZ (habitable zone) – a region around a sun where liquid could be present on the surface, and could contain the elements to support life – was detected only in 1995! The latest: Kepler 186f could be the most probable contender for supporting life due to it being similar in size to Earth; it orbits a red dwarf star 500 light years away.

In addition, two other worlds – 70 Virginis, in the Virgo constellation, & 47 UMa, in Ursa Major, could possess the credentials to support the formation of life, and they are only 35 light years away.

Sorry, but this is what aliens are most likely to resemble...
Sorry, but this is what aliens are most likely to resemble…

“There is nothing special about Earth. If life can arise on one planet around one star in one galaxy, then it could happen on billions of such planets” – Tim Radford.  

The quest for extraterrestrial life has bamboozled terrestrial science (and philosophy) since time immemorial. Lucretius, the Roman philosopher wote about the “seeds of life” floating through space in his: De Rerum Naturae. This concept became known as “Panspermia” and was later discussed by Svante Arhenius (a Swedish Nobel prize-winner) and Sir Fred Hoyle ( a British astronomer). Thomas Jefferson, founding father and president of the United States, speculated about life on other planets, but only about whether they “had souls to be saved.”

Then, with H G Wells, there were aliens – from Mars, our nearest neighbour – but they did not come in peace. In the last century, as science fiction has rocketed (sorry), there has been all sorts of long and short, green and blue, bug-eyed and three-fingered “visitors” from a vast array of weird and wonderful alien worlds.

Everyone is familiar with the five-year mission objective of the original (endearingly daft) Star Trek series but nothing in my vast reams of research can elucidate why so much of that “strange new life” (predominantly carbon-based, of course) had to have weird knobs, crests, and even trilobytes stuck to their foreheads. Gene Roddenberry certainly moved in mysterious ways…

We are finding exoplanets "by the bus load" now
We are finding exoplanets “by the bus load” now

“If there are creatures there they are going to be short and fat, not long and thin like us. They will be more like crabs than sheep and would move by scuttling sideways” – Dr Paul Murdin, British National Space Centre.

Humanoid aliens are so common (not just because of limitations of cheap sfx) but because eyes, mouths and limbs are essential components of any (not all) living organisms. Yet modern exobiologists recognise that carbon, hydrogen and oxygen don’t need to be mandatory building blocks for life; silicon could be vital as well.   

Unfortunately, Science presents us with a less exciting image of aliens. Extraterrestrials – if they are to be found at all – would have to adapt to massive gravity, be of small and very flat shape, with a protective carapace, very much like a limpet. The conditions for complex chemicals to turn into complex self-replicating proteins and then cells have to be precise.

But what triggers those conditions? And where can we find them?  

On a final note, there was an amusing two-page story in Mystery in Space comic (1981) in which first contact is made on a distant planet by three Earth astronauts with a race of green, long-necked tortoise-like creatures. The translator is opened (on all frequencies, of course) and the Commander greets them. No reply; not even a sound. The aliens just ignore them, trudging along the streets of their great city. Dejected, the humans pack up and leave. As their spaceship blasts back into the heavens, one alien turns to his chum and says:

” Thank Drok! I thought they’d never leave!”   

The second alien replies: “Yeah, blasted tourists, who needs ’em?”

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