Planet theorists are putting up a valiant fight against new findings, but in some cases, the evidence seems to be winning.
Moon. “New research provokes more questions about the origin of the moon,” blazes a headline on PhysOrg from last month. For some time now, the “favored scenario” for our moon’s origin has been that a Mars-size body impacted the earth, and the moon formed from the debris. Scientists even gave a mythical name to the impactor: Theia. Trouble is, Theia might really be just a myth:
Now, new research from geophysical scientist Junjun Zhang and colleagues, suggests that such thinking might be wrong. In their paper published in Nature Geoscience, they find that in comparing titanium isotopes from both the moon and the Earth, that the match is too close to support the theory that the moon could have been made partly of material from another planet.
The match of isotopes between Earth and moon is too close to believe that a distant impactor brought material from elsewhere. But it is even more implausible to imagine Earth spinning so fast to throw off some of its material to form the moon. This leaves mythmakers in an a-musing paradox: “Hopefully new research will one day provide us with a definitive answer. Until that day though, it seems we will all have to just keep on musing.”
Mars: The dry-Marsers scored more points over the wet-Marsers this month. In Nature News (April 11), Eric Hand wrote an article entitled, “Dreams of water on Mars evaporate: Climate models reveal the red planet was mostly cold and dry.” The pendulum has swung back to the dry-Marsers:
Last month, Jim Head, a planetary scientist at Brown University in Providence, Rhode Island, threw a wet blanket on the idea that Mars was ever very wet at all, in a keynote talk at the Lunar and Planetary Science Conference in The Woodlands, Texas. Head and others are assembling a picture of a Mars that was cold and dry from the beginning, punctuated at most by short bursts of wetness. “The notion of a palm-tree-covered Mars has waned,” says Stephen Clifford, a planetary scientist at the Lunar and Planetary Institute in Houston, Texas, who is organizing a conference in May on the early climate of Mars.
Head’s “revisionism” is driving Mars lifers into hiding: “[Jeff] Andrews-Hanna [Colorado School of Mines] says the shift in thinking doesn’t rule out life on ancient Mars, but instead drives it deeper underground.”
A paper in Science today (27 April 2012: Vol. 336 no. 6080 pp. 449-452, DOI: 10.1126/science.1219437) doesn’t need Martian water, either. Strange-looking polygons and coils in Athabasca Valles were explained by Phil Christensen and Andrew Ryan as artifacts of lava flows. The spiral coils found by Ryan on HiRise photos from the Mars Reconnaissance Orbiter (see photo on National Geographic News) are like fossil eddies created by shear stress in the flowing pahoehoe lava (see Science Daily). They don’t require water or ice for their formation. Moreover, they formed quickly:
Ice-related processes fail to account for our observations. There are no known mechanisms to naturally produce spiral patterns in ice-rich environments on the scale and frequency observed in our study area. If the primary plates were ice rafts, then the water extruded during rafting would not have the correct viscosity to form and preserve the coils. We have also shown that the polygons formed after the fracture and drift of the secondary plates on which they are present. This precludes the notion that the polygons formed over decades or even centuries in an ice-rich regolith, because it seems unlikely that frozen soil could somehow fracture and drift.
Late Heavy Bombardment. The notion of a “Late Heavy Bombardment” (LHB) of the inner solar system (1/09/2012, 9/17/2010, 2/16/2010) long after the birth of Earth is taking some bombardment of its own. The “spotty impact record” on the moon is making it difficult to maintain that a stream of high-velocity impactors came in a barrage about 4 million years ago; crater data seem to indicate a mix of high-velocity and low-velocity impactors. Richard A. Kerr in Science (13 April 2012: Vol. 336 no. 6078 p. 151, DOI: 10.1126/science.336.6078.151-b) reported on the controversy at the Lunar and Planetary Science Conference where, at a pre-conference workshop, William Bottke tried to be diplomatic. To keep peace between the catastrophists (who believe in the LHB) and the pacifists (who assert that most cratering tapered off after the birth of the inner planets), Bottke suggested both groups might be partly right.
At the conference, Bottke presented a blend of the competing bombardment histories that takes account of the spotty impact record produced by a mix of fast and slow impacters…. Bottke thinks the resulting late bombardment was longer and less intense than many catastrophists have proposed.
Kerr did not indicate if everybody is happy with the compromise.
Nebular hypothesis: More new troubles are brewing for old ideas that debris disks around stars are nurseries for planets. The old picture was that dust is hot near the star, but frozen at the outer edge of the disk. A “frost line” in the middle segregates rocky from volatile material that presumably remains frozen in its primordial state. Alas, more evidence has come in that complicates the picture. A study reported by the Harvard-Smithsonian Center for Astrophysics, echoed on PhysOrg, indicates that some of the outermost material of dust disks must have melted. Infrared measurements can differentiate between amorphous and crystalline dust. Primordial dust is assumed to have been amorphous. To have become crystalline, as the data from the Spitzer Space Telescope indicated, the outermost dust must have heated up to the melting point and re-frozen. This echoes observations from comets, once thought to be primordial snowballs from the edges of our solar system, but have been observed to contain high-melting-point ingredients (4/18/2011).
Theorists are stuck with two possibilities: the dust migrated from the inner regions outward by some unknown mechanism, or another unknown mechanism (perhaps a shock wave) heated the material in the outer regions. The press release put the best possible spin on this new puzzle: “The new paper answers some questions while refining others, and is a good example of the important progress being made today in understanding how planets and planetary systems form.” Being interpreted, this means, “We haven’t a clue, but science marches on.”
Cosmic rays: Another theory on a cosmic scale took a big hit this month with no replacement paradigm in sight. Astronomers had hoped to explain high-energy cosmic rays as coming from some of the most energetic events known to occur in the universe: gamma-ray bursts (GRBs). New measurements from a large neutrino detector embedded in Antarctic ice (appropriately named IceCube) failed to correlate detector flashes with the short-lived bursts. The report in Nature (484, 19 April 2012, pp. 351–354, doi:10.1038/nature11068) left explanations hanging:
This implies either that GRBs are not the only sources of cosmic rays with energies exceeding 1018 electronvolts or that the efficiency of neutrino production is much lower than has been predicted.
Observations were 3.6 times lower than predicted by theory. Space.com titled its report, “Cosmic Ray Mystery Leaves Scientists in the Dark.” PhysOrg headlined, “Neutrinos put cosmic ray theory on ice.”
These reports might support scientific progress by falsification: i.e., that science progresses by ruling out theories. It’s helpful to know that some popular theories are no longer supportable by new evidence, but scientific understanding cannot grow by subtraction alone. When what we think we know turns out to be false, can scientists really claim to understand the world? An article on Evolution News & Views questions whether “known knowns” are progressing against “known unknowns,” “unknown unknowns” and “unknowable unknowns” – and whether positivists like Michael Shermer have a clue where the boundary lies between knowledge and ignorance.
We certainly applaud the teams that build, operate and collect data from intelligently-designed instruments like Spitzer, IceCube and Mars Reconnaissance Orbiter. Data from these amazing instruments are a gift bequeathed to us in the information age. We only point out that good data are a necessary, but not sufficient, condition for scientific understanding. Time after time, we provide examples in these pages of predictions, expectations and favored theories that are suffering a late heavy bombardment of high-speed data impactors. Maybe it will dawn on some readers that the consensus worldview, the bottom-up, naturalistic evolutionary assumption, is a detriment to scientific understanding.