In most careers, being wrong too often is grounds for dismissal. False prophets in ancient kingdoms were stoned or shamed out of town. Only in science, it seems, can experts consistently get it wrong, and not only keep their jobs, but be highly esteemed as experts. Among the guiltiest of the lot are planetary scientists, whose predictions have been consistently wrong for almost every planetary body studied since the dawn of the space age. Their orbital mechanics is solid; they do get their spacecraft to arrive at the right place at the right time with uncanny accuracy. But what the missions reveal is often completely different from what scientists had told the public they expected to find. This has been true of Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, comets, asteroids, and most of the moons of the solar system, where hasty revisions have had to be made after spacecraft data falsified the predictions. Here are some recent examples of “theory fail” in planetary science.
Sun: The Genesis spacecraft was supposed to tell planetary scientists how the rocky planets formed by gathering particles from the solar wind and comparing its isotopes with those of the planets. Theory assumed that the earth, having formed from the primordial nebula surrounding the parent star, would have similar isotopic signatures to the sun. Analysis of the data was seriously delayed due to the catastrophic crash landing of the capsule in 2004. Results were just published in two papers in Science.1,2 Specifically, the sun’s particles were found to have much more oxygen-16 and dramatically less nitrogen-14 than is found in Earth’s atmosphere. Commenting on this surprise, Science Daily titled its report, “Sun and Planets Constructed Differently Than Thought, NASA Mission Suggests.”
Commenting on these papers in the same issue of Science,3 Robert Clayton said, “The principal conclusion from the studies of McKeegan et al. and Marty et al. is that the Earth was not constructed from average solar system materials.” A hastily-concocted scenario involving self-shielding of isotopes was put forth to explain the discrepancy, but Space.com reminded readers, “it’s not a certainty.” Bernard Marty, lead author of one of the papers, said in Science Daily, “These findings show that all solar system objects including the terrestrial planets, meteorites and comets are anomalous compared to the initial composition of the nebula from which the solar system formed. Understanding the cause of such a heterogeneity will impact our view on the formation of the solar system.” Another article on Science Daily put a happy face on the problem with this headline: “Solar Wind Samples Give Insight Into Birth of Solar System.”
Enceladus: Saturn’s geysering moon Enceladus has become a prima donna of the solar system with its dramatic performances. The Cassini spacecraft recently made another pass through the geysers at close range and sampled some of the particles (see Science Daily, Physorg). New counts of sodium and potassium particles are swinging opinion in favor of a liquid-water ocean down deep. This, predictably, stimulated rhetoric about the L-word life, as Richard Kerr shamelessly shouted in his headline in Science last week,4 “Enceladus Now Looks Wet, So It May Be ALIVE!”
The real headline, though, is that water was unexpected at this tiny moon the diameter of Arizona. In another article on Science Daily, Nicholas Altobelli lamented, “Enceladus is a tiny icy moon located in a region of the outer Solar System where no liquid water was expected to exist, because of its large distance from the Sun.” He, too, quickly changed the subject to life: “This finding is therefore a crucial new piece of evidence showing that environmental conditions favourable to the emergence of life may be sustainable on icy bodies orbiting gas giant planets.”
The life word cannot mask the challenge that Enceladus makes to claims that it is 4.6 billion years old. A new paper in Icarus emphasizes the problem: Chin and Nimmo calculated that obliquity tides do not significantly heat Enceladus. Any heating would be around a thousand times too small as a heat source for the moon’s powerful geysers.5
Incidentally, readers may wish to gaze upon a dazzling close-up of the tiny moonlet Helene taken by the Cassini orbiter on June 18 (Space.com).
Comets: It wasn’t that many years ago that scientists were telling the public that comets were dirty snowballs from the pristine outer reaches of the solar system nudged in toward the sun by passing stars. Several missions to real comets, including Halley, Borrely, and Tempel 1, have shown that idea to be simplistic. Minerals requiring high temperatures for their formation were found from the Deep Impact experiment, and Stardust found similar anomalous materials, calling for radical revisions of theories.
Now enter Comet Hartley 2, visited last November on Deep Impact’s extended mission, nicknamed EPOXI. Natalie Wolchover’s headline on Live Science tells all: “Quirky Comet Hartley 2 Confounds Theories on Early Solar System.” This oddball comet is not only hyperactive and spinning rapidly (contrary to expectations), it has different levels of carbon monoxide on the two ends of its peanut shape, spits off large chucks of ice, and has CN values that varied dramatically during the observation period.
The summary and conclusions of a paper in Science6 revealed face-saving rhetoric: “Comet 103P/Hartley 2 differs in many ways from 9P/Tempel 1 and is an ideal example of hyperactive comets, ones that produce more H2O per unit time than should be possible by sublimation from the small surface area of their nuclei.” This seems to be saying that the comet is an ideal example of an impossible object. The description continued, calling attention to other unexected differences with other comets, ending, “A large anomaly in CN, too slow to be called an outburst, is unexplained.”
1. Marty et al, “A 15N-Poor Isotopic Composition for the Solar System As Shown by Genesis Solar Wind Samples ” Science, 24 June 2011: Vol. 332 no. 6037 pp. 1533–1536, DOI: 10.1126/science.1204656.
2. McKeegan et al, “The Oxygen Isotopic Composition of the Sun Inferred from Captured Solar Wind,” Science, 24 June 2011: Vol. 332 no. 6037 pp. 1528–1532, DOI: 10.1126/science.1204636.
3. Robert Clayton, “Planetary Science: The Earth and the Sun,” Science, 24 June 2011: Vol. 332 no. 6037 pp. 1509–1510, DOI: 10.1126/science.1206965.
4. Richard A. Kerr, “Planetary Science Enceladus Now Looks Wet, So It May Be ALIVE!”, Science, 10 June 2011: Vol. 332 no. 6035 p. 1259, DOI: 10.1126/science.332.6035.1259.
5. Chin and Nimmo, “Obliquity tides do not significantly heat Enceladus,” Icarus (article in press June 2011), doi:10.1016/j.icarus.2011.06.007.
6. A’Hearn et al, “EPOXI at Comet Hartley 2,” Science, 17 June 2011: Vol. 332 no. 6036 pp. 1396–1400, DOI: 10.1126/science.1204054.
We want to make it clear that this is not a criticism of scientific discovery, but of scientific explanation. The thousands of scientists, engineers and technicians who make these spacecraft work are to be forever commended for bringing to earth, in our lifetimes, a hugely impressive treasure trove of new data about the solar system. This includes the technicians who tirelessly worked for years to save the delicate particles from the Genesis mission, and all the others who have wrought success after success with Stardust, Cassini, Deep Impact, and all the other heroic missions of discovery.
Explanation, however, is a completely different thing. Because of their evolutionary old-age assumptions, planetary scientists expected to find things in keeping with their assumptions. When they didn’t, should they be praised? Numerous findings have falsified their evolutionary picture. Their web of belief has had to be reinforced with steel to protect the all-important central assumption of the A.S.S. (age of the solar system, 4.6 billion years), the Law of the Misdeeds and Perversions that Cannot Be Altered. Don’t be distracted by their red herrings about life. The Baloney Detector pointer dog is no respecter of persons: ’You were wrong!” he barks.