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Artist's impression of gas and dust - the raw materials for making planets - swirl around a young star. The planets in our solar system formed from a similar disk of gas and dust captured by our sun. Credit: NASA/JPL-Caltech. |
Contrary to the creationist fantasy that there is something special about Earth which makes it the only place in the Universe where intelligent life could live, and where everything is 'just right' for humans, a paper presented to the National Astronomy Meeting in Llandudno, Wales last Wednesday by Prof Brad Gibson, of the University of Hull, showed how Earth-like planets are very probably the norm in solar systems in the Milky Way galaxy.
Minerals made from building blocks of carbon, oxygen, magnesium, and silicon are thought to control the landscape of rocky planets that form in solar systems around Sun-like stars. A subtle difference in mineralogy can have a big effect on plate tectonics, and heating and cooling of the planet’s surface, all of which can affect whether a planet is ultimately habitable. Until now, astronomers thought that rocky planets fell into three distinct groups: those with a similar set of building blocks to Earth, those that had a much richer concentration of carbon, and those that had significantly more silicon than magnesium.
“The ratio of elements on Earth has led to the chemical conditions ‘just right’ for life. Too much magnesium or too little silicon and your planet ends up having the wrong balance between minerals to form the type of rocks that make up the Earth’s crust,” said Gibson. “Too much carbon and your rocky planet might turn out to be more like the graphite in your pencil than the surface of a planet like the Earth.”
Gibson and team from the E.A. Milne Centre for Astrophysics at the University of Hull have constructed a sophisticated simulation of the chemical evolution of the Milky Way, which results in an accurate recreation of the Milky Way as we see it today. This has allowed them to zoom in and examine the chemistry of processes, such as planetary formation, in detail. Their findings came as something of a surprise.
“At first, I thought we’d got the model wrong!” explained Gibson. “As an overall representation of the Milky Way, everything was pretty much perfect. Everything was in the right place; the rates of stars forming and stars dying, individual elements and isotopes all matched observations of what the Milky Way is really like. But when we looked at planetary formation, every solar system we looked at had the same elemental building blocks as Earth, and not just one in three. We couldn't find a fault with the model, so we went back and checked the observations. There we found some uncertainties that were causing the one-in-three result. Removing these, observations agreed with our predictions that the same elemental building blocks are found in every exoplanet system, wherever it is in the galaxy.”
The cloud out of which the solar system formed has approximately twice as many atoms of oxygen as carbon, and roughly five atoms of silicon for every six of magnesium. Observers trying to ascertain the chemical make-up of planetary systems have tended to look at large planets orbiting very bright stars, which can lead to uncertainties of 10 or 20 per cent. In addition, historically the spectra of oxygen and nickel have been hard to differentiate. Improvements in spectroscopy techniques have cleaned up the oxygen spectra, providing data that matches the Hull team’s estimates.
“Even with the right chemical building blocks, not every planet will be just like Earth, and conditions allowing for liquid water to exist on the surface are needed for habitability,” said Gibson. “We only need to look to Mars and Venus to see how differently terrestrial planets can evolve. However, if the building blocks are there, then it’s more likely that you will get Earth-like planets – and three times more likely than we’d previously thought.”
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Rich spectrum of colours in the rocks around the Mutnovsky and Gorley volcanoes on the Kamchatka Peninsula. The mineralogy of rocks on Earth provide the chemical building blocks needed for life. Credit: Europlanet/A. Samper |
But don't worry if you're a fan of it; the fact of having a notion falsified is never regarded as a bar to trying to get away with it on someone more ignorant or more gullible in creationism and religious apologetic circles. You can be fairly sure this claim will still be around in ten, twenty, maybe thirty years time if there are enough credulous people still capable of being fleeced as there almost certainly will in the more backward parts of the world.
The problem is, creationism is not based on real world observations like science is. With science the conclusion always flows from and is led by the evidence. Until there is enough evidence there is no conclusion and when the evidence changes, the conclusion is changed accordingly.
With creationism, the conclusion is fixed and unchangeable and has nothing to do with evidence. Evidence is alway subservient to that sacred conclusion and can be dismissed or denied at will to keep the sacred conclusion in tact.
Don't take my word for this but spend a few minutes on any creationist social networking site or visit one of the creationist industry's sales outlets posing as creation 'science' sites. The one thing that can't be contemplated is the dogma that the Bronze-Age goat-herders who thought up the biblical creation myth could possibly have been wrong. Whatever they said trumps all the science, all the evidence, all the logic and all the deductive reasoning that you can throw at it. Nothing on Earth would induce a creationist to change his/her mind.
So creationists will continue arguing that there is something special and magical about Earth that could only have been due to their particular supernatural magic friend, not because the evidence says so and despite the fact hat the evidence refutes it. They will continue to argue for the 'Goldilocks' fairy tale not because it is true but because they would like it to be true. Facts don't matter to creationism.
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