Get a grip. A new robotic gripping tool based on gecko feet can grab hold of floating objects in microgravity. The grippers could one day help robots move dangerous space junk to safer orbits or climb around the outside of space stations.

Most strategies for sticking don’t work in space. Chemical adhesives can’t withstand the wide range of temperatures, and suction doesn’t work in a vacuum.

Adhesives inspired by gecko feet — which use van der Waals forces to cling without feeling sticky (SN Online: 11/18/14) — could fit the bill, says Mark Cutkosky of Stanford University, whose team has been designing such stickers for more than a decade. Now his team has built robotic gripper “hands” that can grapple objects many times their size without pushing them away, the researchers report June 28 in Science Robotics.
The team first tested the grippers in the Robo-Dome, a giant air hockey table at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., where two 370-kilogram robots gently pushed each other around using a small square of gecko gripper.

Then last summer, Aaron Parness and Christine Fuller, of the Jet Propulsion Lab, and Hao Jiang of Stanford took the full gripper hand, which includes several patches of gripping material in a specific arrangement, on a microgravity flight in NASA’s Weightless Wonder aircraft. The team used the hand to grab and release a cube, cylinder and beach ball, which represented satellites, spent rockets or fuel tanks, and pressure vessels.

Gripper hands could be used to repair or move dead satellites, or help miniature satellites called CubeSats stick to larger spacecraft like barnacles, Parness says.

Hominid hubbub
In “Hominid roots may go back to Europe” (SN: 6/24/17, p. 9), Bruce Bower reported that the teeth of Graecopithecus, a chimp-sized primate that lived in southeastern Europe 7 million years ago, suggest it was a member of the human evolutionary family.

“Is it appropriate to use the terms ‘hominid’ and ‘ape’ as if the two are mutually exclusive categories?” asked online reader Tim Cliffe. “The distinction being made is between our clade in particular and all other apes. It seems to me that ‘hominids’ should be described as a subset of apes, not a separate category,” he wrote.
“Yes, hominids are apes,” Bower says. “The terminology gets pretty thick in evolutionary studies, so researchers (and journalists) use some shortcuts.”

Fossils of many ancient apes dating to between 25 million and 5 million years ago have been found, but the interest in this case is in a key transition to a particular kind of ape that walked upright and displayed various skeletal traits similar to traits unique to the human evolutionary family. “That’s why one source in the story, Bernard Wood, wonders whether Graecopithecus was an apelike hominid or a hominid-like ape,” Bower says. “But it’s important to remember that hominids diverged from other, ancestral apes. So did chimps.”

Science News defines “hominid” as a member of the human evolutionary family.

Laser, camera, action
The world’s fastest video camera films 5 trillion frames every second, Ashley Yeager reported in “A different kind of camera captures speedy actions” (SN: 6/24/17, p. 5). The camera works by flashing a laser at a subject and using a computer program to combine the still images into a video. Researchers tested the device by filming particles of light as the particles traveled a short distance.

Online reader JHoughton1 wondered if the researchers really filmed a light particle in their tests. “I thought light ‘sometimes behaves like a wave, sometimes like a particle,’ but that there isn’t really any particle that’s a particle in the usual sense. Is this really a picture of a ‘particle’ of light? A photon-as-ball-of-stuff?”

The camera captured the forward progression of a laser pulse, which is an ensemble of photons, Yeager says.

Photons themselves aren’t “balls of stuff” on quantum scales, says physics writer Emily Conover. All particles, including photons, are spread out in space, propagating like waves. “Only when scientists measure or observe a photon or any other particle do they find it in one place, like the ball of stuff that people typically imagine. I think in that sense, photons are about as tangible as any other quantum particle,” Conover says.

Bringing down the mucus house
Little-known sea animals called giant larvaceans can catch a lot of carbon in disposable mucus casings called “houses,” Susan Milius reported in “ ‘Mucus houses’ catch sea carbon fast” (SN: 6/10/17, p. 13).

Online reader Robert Stenton wondered what happens to mucus houses as they fall to the bottom of the ocean.

What happens to discarded houses isn’t yet clear, Milius says, though researchers have proposed that the houses might carry substantial portions of carbon to life on the sea bottom. And if bits of a house fall fast enough to reach great depths, the carbon could get trapped in water masses that move around the planet for centuries before surfacing. Bits drifting down slowly may be intercepted by microbes and other debris feeders and would not end up sequestered.

Correction
In “Human noises invade wilderness” (SN: 6/10/17, p. 14), Science News incorrectly reported that official wilderness areas in the United States do not allow livestock grazing. Grazing is permitted in protected wilderness areas at preprotection levels under the Wilderness Act of 1964, which created the National Preservation System.

A 13-million-year-old infant’s skull, discovered in Africa in 2014, comes from a new species of ape that may not be far removed from the common ancestor of living apes and humans.

The tiny find, about the size of a lemon, is one of the most complete skulls known of any extinct ape that inhabited Africa, Asia or Europe between 25 million and 5 million years ago, researchers report in the Aug. 10 Nature. The fossil provides the most detailed look to date at a member of a line of African primates that are now candidates for central players in the evolution of present-day apes and humans.
Most fossils from more than 40 known extinct ape species amount to no more than jaw fragments or a few isolated teeth. A local fossil hunter spotted the nearly complete skull in rock layers located near Kenya’s Lake Turkana. Members of a team led by paleoanthropologist Isaiah Nengo estimated the fossil’s age by assessing radioactive forms of the element argon in surrounding rock, which decay at a known rate.

Comparisons with other African ape fossils indicate that the infant’s skull belongs to a new species that the researchers named Nyanzapithecus alesi. Other species in this genus, previously known mainly from jaws and teeth, date to as early as around 25 million years ago.

“This skull comes from an ancient group of apes that existed in Africa for over 10 million years and was close to the evolutionary origin of living apes and humans,” says Nengo, of Stony Brook University in New York and De Anza College in Cupertino, Calif.

He and colleagues looked inside the skull using a powerful type of 3-D X-ray imaging. This technique revealed microscopic enamel layers that had formed daily from birth in developing adult teeth that had yet to erupt. A count of those layers indicates that the ape was 16 months old when it died.

Based on a presumably rapid growth rate, the scientists calculated that the ancient ape would have weighed about 11.3 kilograms as an adult. Its adult brain volume would have been almost three times larger than that of known African monkeys from the same time, the researchers estimate.
N. alesi’s tiny mouth and nose, along with several other facial characteristics, make it look much like small-bodied apes called gibbons. Faces resembling gibbons evolved independently in several extinct monkeys, apes and their relatives, the researchers say. The same probably held for N. alesi, making it an unlikely direct ancestor of living gibbons, they conclude.
No lower-body bones turned up with the new find. Even so, it’s possible to tell that N. alesi did not behave as present-day gibbons do. In gibbons, a part of the inner ear called the semicircular canals, which coordinates balance, is large relative to body size. That allows the apes to swing acrobatically from one tree branch to another. N. alesi’s small semicircular canals indicate that it moved cautiously in trees, Nengo says.

Several of the infant skull’s features, including those downsized semicircular canals, connect it to a poorly understood, 7-million- to 8-million-year-old ape called Oreopithecus. Fossils of that primate, discovered in Italy, suggest it walked upright with a slow, shuffling gait. If an evolutionary relationship existed with the older N. alesi, the first members of the Oreopithecus genus probably originated in Africa, Nengo proposes.

Without any lower-body bones for N. alesi, it’s too early to rule out the possibility that Nyanzapithecus gave rise to modern gibbons and perhaps Oreopithecus as well, says paleontologist David Alba of the Catalan Institute of Paleontology Miquel Crusafont in Barcelona. Gibbon ancestors are thought to have diverged from precursors of living great apes and humans between 20 million and 15 million years ago, Alba says.

Despite the age and unprecedented completeness of the new ape skull, no reported tooth or skull features clearly place N. alesi close to the origins of living apes and humans, says paleoanthropologist David Begun of the University of Toronto.

Further studies of casts of the inner braincase, which show impressions from surface features of the brain, may help clarify N. alesi’s position in ape evolution, Nengo says. Insights are also expected from back, forearm and finger fossils of two or three ancient apes, possibly also from N. alesi, found near the skull site in 2015. Those specimens also date to around 13 million years ago.

On the morning of August 21, a pair of jets will take off from NASA’s Johnson Space Center in Houston to chase the shadow of the moon. They will climb to 15 kilometers in the stratosphere and fly in the path of the total solar eclipse over Missouri, Illinois and Tennessee at 750 kilometers per hour.

But some of the instruments the jets carry won’t be looking at the sun, or even at Earth. They’ll be focused on a different celestial body: Mercury. In the handful of minutes that the planes zip along in darkness, the instruments could collect enough data to answer this Mercury mystery: What is the innermost planet’s surface made of?
Because it’s so close to the sun, Mercury is tough to study from Earth. It’s difficult to observe close up, too. Extreme heat and radiation threaten to fry any spacecraft that gets too close. And the sun’s brightness can swamp a hardy spacecraft’s efforts to send signals back to Earth.

NASA’s Messenger spacecraft orbited Mercury from 2011 to 2015 and revealed a battered, scarred landscape made of different material than the rest of the terrestrial planets (SN: 11/19/11, p. 17).
But Messenger only scratched the surface, so to speak. It analyzed the planet’s composition with an instrument called a reflectance spectrometer, which collects light and then splits that light into its component wavelengths to figure out which elements the light was reflected from.
Messenger took measurements of reflected light from Mercury’s surface at wavelengths shorter than 1 micrometer, which revealed, among other things, that Mercury contains a surprising amount of sulfur and potassium (SN: 7/16/11, p. 12). Those wavelengths come only from the top few micrometers of Mercury. What lies below is still unknown.

To dig a few centimeters deeper into Mercury’s surface, solar physicist Amir Caspi and planetary scientist Constantine Tsang of the Southwest Research Institute in Boulder, Colo., and colleagues will use an infrared camera, specially built by Alabama-based Southern Research, that detects wavelengths between 3 and 5 micrometers.

Copies of the instrument will fly on the two NASA WB-57 research jets, whose altitude and speed will give the observers two advantages: less atmospheric interference and more time in the path of the eclipse. Chasing the moon’s shadow will let the planes stay in totality — the region where the sun’s bright disk is completely blocked by the moon — for a combined 400 seconds (6.67 minutes). That’s nearly three times longer than they would get by staying in one spot.
Mercury’s dayside surface is 425° Celsius, and it actually emits light at 4.1 micrometers — right in the middle of the range of Caspi’s instrument. As any given spot on Mercury rotates away from the sun, its temperature drops as low as ‒179° C. Measuring how quickly the planet loses heat can help researchers figure out what the subsurface material is made of and how densely it’s packed. Looser sand will give up its heat more readily, while more close-packed rock will hold heat in longer.

“This is something that has never been done before,” Caspi says. “We’re going to try to make the first thermal image heat map of the surface of Mercury.”

Unfortunately for Caspi, only two people can fly on the jet: The pilot and someone to run the instrument. Caspi will remain on the ground in Houston, out of the path of totality. “So I will get to watch the eclipse on TV,” Caspi says.

Every few years, for a handful of minutes or so, science shines while the sun goes dark.

A total eclipse of the sun is, for those who witness it, something like a religious experience. For those who understand it, it is symbolic of science’s triumph over mythology as a way to understand the heavens.

In ancient Greece, the pioneer philosophers realized that eclipses illustrate how fantastic phenomena do not require phantasmagoric explanation. An eclipse was not magic or illusion; it happened naturally when one celestial body got in the way of another one. In the fourth century B.C., Aristotle argued that lunar eclipses provided strong evidence that the Earth was itself a sphere (not flat as some primitive philosophers had believed). As the eclipsed moon darkened, the edge of the advancing shadow was a curved line, demonstrating the curvature of the Earth’s surface intervening between the moon and sun.

Oft-repeated legend proclaims that the first famous Greek natural philosopher, Thales of Miletus, even predicted a solar eclipse that occurred in Turkey in 585 B.C. But the only account of that prediction comes from the historian Herodotus, writing more than a century later. He claimed that during a fierce battle “day suddenly became night,” just as Thales had forecast would happen sometime during that year.

There was an eclipse in 585 B.C., but it’s unlikely that Thales could have predicted it. He might have known that the moon blocks the sun in an eclipse. But no mathematical methods then available would have allowed him to say when — except, perhaps, a lucky coincidence based on the possibility that solar eclipses occurred at some regular cycle after lunar eclipses. Yet even that seems unlikely, a new analysis posted online last month finds.

“Some scholars … have flatly denied the prediction, while others have struggled to find a numerical cycle by means of which the prediction could have been carried out,” writes astronomer Miguel Querejeta. Many such cycles have already been ruled out, he notes. And his assessment of two other cycles concludes “that none of those conjectures can be regarded as serious explanations of the problematic prediction of Thales: in addition to requiring the existence of long and precise eclipse records … both cycles that have been examined overlook a number of eclipses which match the visibility criteria and, consequently, the patterns suggested seem to disappear.”

It’s true that the ancient Babylonians worked out methods for predicting lunar eclipses based on patterns in the intervals between them. And the famous Greek Antikythera mechanism from the second century B.C. seems to have used such cycle data to predict some eclipses.

Ancient Greek astronomers, such as Hipparchus (c. 190–120 B.C.), studied eclipses and the geometrical relationships of the Earth, moon and sun that made them possible. Understanding those relationships well enough to make reasonably accurate predictions became possible, though, only with the elaborate mathematical description of the cosmos developed (drawing on Hipparchus’ work) by Claudius Ptolemy. In the second century A.D., he worked out the math for explaining the movements of heavenly bodies, assuming the Earth sat motionless in the center of the universe.

His system specified the basic requirements for a solar eclipse: It must be the time of the new moon — when moon and sun are on the same side of the Earth — and the positions of their orbits must also be crossing the ecliptic, the plane of the sun’s apparent orbital path through the sky. (The moon orbits the Earth at a slight angle, crossing the plane of the ecliptic twice a month.) Only precise calculations of the movements of the sun and moon in their orbits could make it possible to predict the dates for eclipsing alignments.

Predicting when an eclipse will occur is not quite the same as forecasting exactly where it will occur. To be accurate, eclipse predictions need to take subtle gravitational interactions into account. Maps showing precisely accurate paths of totality (such as for the Great American Eclipse of 2017) became possible only with Isaac Newton’s 17th century law of gravity (and the further development of mathematical tools to exploit it). Nevertheless Ptolemy had developed a system that, in principle, showed how to anticipate when eclipses would happen. Curiously, though, this success was based on a seriously wrong blueprint for the architecture of the cosmos.

As Copernicus persuasively demonstrated in the 16th century, the Earth orbits the sun, not vice versa. Ptolemy’s geometry may have been sound, but his physics was backwards. While demonstrating that mathematics is essential to describing nature and predicting physical phenomena, he inadvertently showed that math can be successful without being right.

It’s wrong to blame him for that, though. In ancient times math and science were separate enterprises (science was then “natural philosophy”). Astronomy was regarded as math, not philosophy. An astronomer’s goal was to “save the phenomena” — to describe nature correctly with math that corresponded with observations, but not to seek the underlying physical causes of those observations. Ptolemy’s mathematical treatise, the Almagest, was about math, not physics.

One of the great accomplishments of Copernicus was to merge the math with the physical realty of his system. He argued that the sun occupied the center of the cosmos, and that the Earth was a planet, like the others previously supposed to have orbited the Earth. Copernicus worked out the math for a sun-centered planetary system. It was a simpler system than Ptolemy’s. And it was just as good for predicting eclipses.

As it turned out, though, even Copernicus didn’t have it quite right. He insisted that planetary orbits were circular (modified by secondary circles, the epicycles). In fact, the orbits are ellipses. It’s a recurring story in science that mathematically successful theories sometimes are just approximately correct because they are based on faulty understanding of the underlying physics. Even Newton’s law of gravity turned out to be just a good mathematical explanation; the absolute space and invariable flow of time he believed in just aren’t an accurate representation of the universe we live in. It took Einstein to see that and develop the view of gravity as the curvature of spacetime induced by the presence of mass.
Of course, proving Einstein right required the careful measurement by Arthur Eddington and colleagues of starlight bending near the sun during a solar eclipse in 1919. It’s a good thing they knew when and where to go to see it.