Until we learn whether or not life exists on other planets, we extrapolate on the basis of our single living world. Just how long it took life to develop is a vital question, with implications that extend to other planetary systems. In today's essay, Alex Tolley...
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The Ambiguity of Exoplanet Biosignatures
The search for life on planets beyond our Solar System is too often depicted as a binary process. One day, so the thinking goes, we'll be able to directly image an Earth-mass exoplanet whose atmosphere we can then analyze for biosignatures. Then we'll know if there is...
The “Habitability” of Worlds (Part I)
Dave Moore is a Centauri Dreams regular who has long pursued an interest in the observation and exploration of deep space. He was born and raised in New Zealand, spent time in Australia, and now runs a small business in Klamath Falls, Oregon. He counts Arthur C....
Life from Elsewhere
The idea that life on Earth came from somewhere else has intrigued me since I first ran into it in Fred Hoyle's work back in the 1980s. I already knew of Hoyle because, if memory serves, his novel The Black Cloud (William Heinemann Ltd, 1957) was the first science...
Probing the Galaxy: Self-Reproduction and Its Consequences
In a long and discursive paper on self-replicating probes as a way of exploring star systems, Alex Ellery (Carleton University, Ottawa) digs, among many other things, into the question of what we might detect from Earth of extraterrestrial technologies here in the...
The Great Venusian Bug Hunt
Our recent focus on life detection on nearby worlds concludes with a follow-up to Alex Tolley's June essay on Venus Life Finder. What would the sequence of missions look like that resulted in an unambiguous detection of life in the clouds of Venus? To answer that...
Starlight: Toward an Interstellar Biology
If you could send out a fleet of small lightsails, accelerated to perhaps 20 percent of the speed of light, you could put something of human manufacture into the Alpha Centauri triple star system within about 20 years. So goes, of course, the thinking of Breakthrough...
Voice of the (SF) Master: Stanislaw Lem and the Philosophy of SETI
Milan M. ?irkovi?'s work has been frequently discussed on Centauri Dreams, as a glance in the archives will show. My own fascination with SETI and the implications of what has been called 'the Fermi question' led me early on to his papers, which explore the...
Radiolytic H2: Powering Subsurface Biospheres
Although we've been focusing lately on photosynthesis, radiolysis -- the dissociation of molecules by ionizing radiation -- can produce food and energy for life below the surface and in deep oceans. Our interest in surface conditions thus needs to be complemented by...
Are Planets with Continuous Surface Habitability Rare?
Put a rocky, Earth-sized planet in the habitable zone of a Sun-like star, and good things should happen. At least, that seems to be the consensus, and since there are evidently billions of such planets in the galaxy, the chances for complex life seem overwhelmingly...