Comets Are Not Life Givers
Astrobiologists dream of comets as bearers of life in spite of—not because of—the data from Rosetta’s comet.
The Rosetta mission, Science Magazine’s Breakthrough of the Year for 2014, gave bad news to astrobiologists this month. A photo caption in Science Magazine says, “Comet 67P/Churyumov-Gerasimenko has begun to emit jets of water vapor that is unlike the water found in Earth’s oceans” (see 12/11/14). And with the Philae lander going to sleep prematurely, mission scientists were unable to get data on possible organic molecules under the comet’s surface. The “dinosaur eggs” found (Science Mag) have nothing to do with dinosaurs; they are clumps of ice on some part of the comet that a few cosmogonists are speculating might have been “cometesimals,” building blocks of the comet, even though they are larger than predicted. “But we don’t understand them,” one admitted.
In short, nothing about Comet 67P looks lively. Its water could not have given birth to our oceans, and its organic molecule inventory, if any, is unknown. Some gases were detected by the orbiter: “A chemical detector, a sort of robotic nose, on the Rosetta orbiter, has detected some organic chemicals in the cloud around the comet,” Tom Chivers writes in The Telegraph. “According to Taylor, it ‘smells like a stag do‘: urine and alcohol and a sulphurous eggy smell,” not that anything as complex as urine was detected (its “perfume” is just ammonia, hydrogen sulfide, formaldehyde, methanol and a few other simple molecules: see Rosetta Blog).
In spite of this negative data, here’s what some scientists and reporters are saying:
- “…comets might have delivered the building-block elements of life to Earth — an idea anticipated by the French astronomer Camille Flammarion more than a century ago” (Milton Wainwright in Nature)
- Getting the list of comets’ primordial ingredients is important because many scientists think comets helped jump-start life on early Earth with an infusion of water and organic molecules. (Science Magazine)
- Long before I dreamed of becoming a scientist, I wondered why Earth was teeming with life, while Mars was a barren, rocky outpost and Venus was shrouded in a dense atmosphere. Somewhere, I read that comets were the reason. Strike a rocky planet with one volatile- and organic-rich comet and an Earth-like environment results. Two comets produce a Venus. No comets: Mars. Of course, this theory was far too simple to explain the differences in the evolution of the inner planets, but no one had ever explored comets up close to know how they might alter a planet’s composition and history—until now. (Marcia McNutt in Science Magazine, “Breakthrough to Our Origins“)
- Of the molecules smelling like “stag do,” Chivers’ next sentence is: “This is the stuff of life.” (The Telegraph)
- Following the successful Philae mission in November, the lander announced it had found organic molecules – the essential building blocks necessary for life.” (The Daily Mail)
- The orbiter sniffed out substances like water, methane and hydrogen — all molecules that are important to life — in the tenuous atmosphere of the comet. (Space.com)
But if water, methane and hydrogen are “molecules that are important to life,” then every planet around every star becomes a candidate for life, even though life has never been detected beyond the earth.
Those who look for organics in fragments of comets and meteors on the ground may have to be extra careful not to jump to conclusions. Astrobiology Magazine reports that contamination can happen quickly. The Sutter’s Mill meteorite of 2012 contained organics. “However, a key conclusion of the paper, and one that is likely to be of keen interest to astrobiologists, is confirmation that meteorites can become contaminated by Earth-based organics very quickly,” the article warns. “That means scientists must be extra vigilant in identifying and assessing the effects of terrestrial organic contamination of meteoritic samples.” It would be good to know, too, whether amino acids in meteors might racemize (scramble from one-handed to two-handed) over time, since racemization is often assumed to show the amino acids came from space.
Bits are the building blocks of essays, aren’t they? Sand is a building block of brick buildings, isn’t it? Air is a building block of lungs, isn’t it? Why, everything is a building block of everything. The stupidity of this reasoning is self-evident. One might as well say that protons and electrons are building blocks of life; quarks, too. What material substance escapes this chain of inference?
The talk about life, with no clear evidence of it, goes far beyond the actual data. It also masks the important trait of life: its specified complexity in the arrangement of molecules for function. Building blocks decay and fall apart without a builder. No one should care that “many scientists think comets helped jump-start life,” except to pity them for speculative folly, and to have righteous anger that the science journals and media show biased favor toward their fact-free philosophical views. Science is about evidence.