An illustration of an alien exoplanet orbiting a distant star.
Credit: NASA, ESA, and G. Bacon (STScI)
SYDNEY: A mathematical equation that counts habitats suitable for alien life could complement the Drake equation, which estimates the probability of finding intelligent alien beings elsewhere in the galaxy.
That equation, developed in 1960 by U.S. astronomer Frank Drake, estimates the probability of intelligent life existing elsewhere in our galaxy by considering the number of stars with planets that could support life (see "Are we alone?").
The new equation, under development by planetary scientists at the Open University in Milton Keynes, England, aims to develop a single index for habitability based on the presence of energy, solvents such as water, raw materials like carbon and whether or not there are benign environmental conditions.
Input of energy
The draft equation will be presented today at the European Planetary Science Congress in Potsdam, Germany, to garner feedback.
"At present, there is no easy way of directly comparing the suitability of different environments as a habitat for life," said planetary scientist Alex Hagermann, who led the research.
Currently, the experts are focussing on energy, which, in the form of visible and infrared light is important for photosynthesis, but can also come in forms that can harm life, such as UV light and X-rays.
"If you can imagine a planet with a thin atmosphere that lets through some of this harmful radiation, there must be a certain depth in the soil where the 'bad' radiation has been absorbed but the 'good' radiation can penetrate," said Hagermann.
Icy planetesimals
"We are looking to be able to define this optimal habitable region in a way that we can say that it is 'as habitable' or 'less habitable' than a desert in Morocco, for example," he said.
So far there has been some criticism of the approach. Astrobiologist and physicist Paul Davies, of the University of Arizona in Tuscon, said it was a "pointless exercise" as the equation refers only to life as we know it.
"The main thing omitted from the conventional Drake equation is the possibility of life inside icy planetesimals, most of which are rogue objects, untethered to stars. Such life is, however, most unlikely to be intelligent," he said.
How about a citation to a
How about a citation to a research paper here. "Under development" means very little.
carbon based?
I am asuming that they are assuming a carbon based lifeform when defining a suitable habitat. I understand that it is the only form we know; but i wonder if that's the only form that exists. - aditya nath jha
How do we know that life must be water and carbon based?
...aims to develop a single index for habitability based on the presence of energy, solvents such as water, raw materials like carbon and whether or not there are benign environmental conditions.
This earth-centric assumption always surprises me. Given the diversity of environments that support life even on earth, how can we say that presence e.g. water and carbon are essential to life? We know that some earth-based life forms can support prolonged exposure to empty space, without even a planet. Isn't it possible that other compounds beyond water and carbon could create conditions that support (another form of) life?
For me, "life" is about some form of consciousness. Not whether it is DNA based. So lets abandon this common view: "In order to find life, lets look for conditions similar to earths"...
Not the only possible, but most likely
From everything I have read and heard, water isn't absolutely necessary and life mustn't always be carbon-based. However, given the unique properties of water and carbon, by their very chemistry, it is far, far more likely for life to develop based around those two substances. I'm not a chemist, just someone interested in science, but at least with carbon, I recall it has a lot to do with it being able to act as the foundation for a while variety of stable molecules - far more than any other atom. So it's not surprising that amino acids, and the gazillions of proteins, and so on have carbon as their foundation.
I've heard less specifics about liquid water, but it seems to be a similar thing with it being far better than most any other substance for facilitating stable, consistent chemical reactions.
In fact, I recall a podcast I listened to a while back that theorized it might actually be quite common for life to break into the photosynthetic immobile lifeforms and the oxygen-breathing mobile lifeforms due to how those two are great sources of energy but in different ways.
So, it's not just an Earth-centric view, but a realization that it is massively easier for life to form based on carbon in an environment with liquid water. That does not mean that there cannot be life with something other than carbon as its foundation or on worlds without liquid water. But when looking for ANY life out there, it makes sense to focus on what we currently believe to be the vastly more common cases. Unfortunately, that often becomes simplified to "life can only exist with liquid water" rather than "by far most life in the universe is probably carbon-based and has liquid water present".
Not the only possible, but most likely
Only in your experience! Isn't this the point! Our experience is limited to an insignificant understanding of the universe so why would we apply this in a search for life? It's like a goldfish looking for life that must have a glass bowl around it and a carbon based life form coming to feed it once a day, improbable to find and missing the point.
Life as we know it
Interesting all the same. The value of the equation may not seem so much now, but in quantifying the data it can be fine-tuned in coming years. As 'life as we know it' changes in time, so the equation can be altered to reflect what we know. This news sounds more like statistical analysis rather than just an equation.
Reminds me of Asimov's 'X stands for unknown' book (Non-fiction) where he explores the viability of silicon-based life (One of the four science essays in the book). Could that type of life be 'as we know it'?
D. Riggs
Then Where Are They?
The biggest hurdle for the Drake Equation is still in play here. Namely, the Fermi Paradox. If all these civilizations are out there, then at least one, possible more, of them should have colonized the entire galaxy y now.
So where are they?