• Pluto
  • Radio image, top; and visible image, bottom

Ingredients of Life on Comet 67/P

Remember Comet 67P/Churyumov-Gerasimenko? The roughly four-kilometer (2.5-mile) wide “rubber ducky” shaped chunk of ice continues to surprise scientists as it pulls inexorably away from the Sun and returns to the depths of space. Since August 2014, it has been orbited by ESA’s Rosetta spacecraft, which has sent back spectacular images of the comet at its most active and turned a battery of scientific instruments toward the surface.

One of those instruments is ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis), a mass spectrometer which can identify chemical compositions from a distance, and in a paper appearing in Science, Kathrin Altwegg—principal investigator for ROSINA—announced that the instrument has made multiple, unambiguous detections of the amino acid glycine in the comet’s halo of gases, or coma. Commonly found in proteins, glycine sublimates at slightly below 150° Celsius, meaning that little of it is released as gas on the comet’s surface, where the average temperature has been measured at -70° Celsius (-94° Fahrenheit). This would make it difficult to detect, but it was first identified at perihelion, when outgassing from the comet was most intense.

Although hints of glycine were detected in material from Comet 81/P Wild 2 returned to Earth by NASA’s Stardust mission in 2004, the possibility of contamination could never be ruled out. The Rosetta detection is supported by the additional identification of the organic molecules methylamine and ethylamine, which are precursors to forming glycine. Altwegg says, “The simultaneous presence of methylamine and ethylamine, and the correlation between dust and glycine, also hints at how the glycine was formed.”

Rosetta also made the first-ever detection at a comet of phosphorus, a key element found in DNA and RNA. Earlier data from Rosetta revealed that the ratio of hydrogen to a hydrogen isotope called deuterium found in 67/P’s ice was different from that in Earthly H2O, suggesting that comets (or at least comets like 67P) may not have been the main source of water for our planet, as scientists have long thought. However, these recent findings support the theory that comets may have delivered, if not water, key molecules for prebiotic chemistry from deep space. —Bing Quock

Beneath Jupiter’s Clouds

Using radio waves to see beneath Jupiter’s thick clouds, astronomers, led by UC Berkeley’s Imke de Pater, have revealed the massive movement of ammonia gas that underlies the colorful bands, spots and whirling clouds visible to the naked eye.

Using the Very Large Array (VLA) in New Mexico, de Pater and her colleagues were able to measure radio waves as deep as 100 kilometers (60 miles) below the cloud tops. “This region was previously unexplored,” de Pater says. “These observations give us important new information about the temperatures, pressures, and motions of gas at these levels of the atmosphere.”

In order to make sensitive radio images, multi-antenna telescopes such as the VLA must gather the radio waves emitted by an object for a significant amount of time, like a time exposure in a camera. However, Jupiter rotates so swiftly—with a “day” of less than 10 hours—that a conventional radio image would be smeared in just a few minutes.

To overcome this obstacle, the researchers took advantage of the added sensitivity of the upgraded VLA, then developed an innovative data-reduction technique to “unsmear” the data from many hours of observing. The results showed a level of detail that provided new insights into the structure and dynamics of the giant planet's atmosphere.

Jupiter’s familiar light-colored zones and darker belts, visible even through small telescopes, were thought to be well-correlated to radio features, but the new radio images show some similar structures unconnected to visible-light features. The radio images also give evidence of what the scientists think are rising plumes of gas that are part of the wave pattern that produces hot spots in the planet’s atmosphere. The Great Red Spot, perhaps the most famous feature on Jupiter, is also prominent, along with similar, smaller storms, in the radio images.

The observations are being reported just one month before the July 4 arrival at Jupiter of NASA’s Juno spacecraft, which plans, in part, to measure the amount of water in the deep atmosphere where the VLA looked for ammonia. “Maps like ours can help put their data into the bigger picture of what’s happening in Jupiter’s atmosphere,” de Pater says. —Molly Michelson

Pluto’s Heart—Lava Lamp or Boiling Oatmeal?

Scientists, reporting this week in two papers in Nature (here and here), have determined that quilted polygonal features within Pluto’s Sputnik Planum region are potentially icebergs floating in a sea of nitrogen. Combining computer models with topographic and compositional data gathered by NASA’s New Horizons spacecraft last summer, the teams have also discovered the depth of this layer of solid nitrogen ice and how fast that ice is flowing, likening it to a “cosmic lava lamp,” among other things.

“Evidence suggests this could be a roiling sea of volatile nitrogen ice,” says Jay Melosh, of Purdue University. “Imagine oatmeal boiling on the stove; it doesn’t produce one bubble for the entire pot as the heated oatmeal rises to the surface and the cooler oatmeal is pushed down into the depths, this happens in small sections across the pot, creating a quilted pattern on the surface similar to what we see on Pluto. Of course, on Pluto this is not a fast process; the overturn within each unit happens at a rate of maybe two centimeters per year.”

Mission scientists used state-of-the-art computer simulations to show that the surface of Sputnik Planum is covered with icy, churning, convective “cells” 16 to 48 kilometers (10 to 30 miles) across, about 10 kilometers (six miles) deep, and less than one million years old. The findings offer additional insight into the unusual and highly active geology on Pluto and, perhaps, other bodies like it on the outskirts of the Solar System.

“Many people expected Pluto to be a cold, dead world,” Melosh says. “What we’ve discovered through this mission is that cold worlds like Pluto have a different kind of activity that involves materials we think of as gases. This understanding offers a new perspective that cold worlds can be just as active and interesting as our own.” —Molly Michelson

The Universe is Expanding Faster Than Expected

In 1924, Edwin Hubble presented his evidence that there are galaxies far outside the confines of the Milky Way, proving that the Universe consists of more than just the Milky Way and is larger than most astronomers thought. In addition, his research showed that the galaxies are all moving apart—in other words, that the Universe is expanding. Backtracking the motion of the galaxies, astronomers say that the expansion began about 13.8 billion years ago. Since Hubble’s time, one of the “Holy Grails” of astronomy has been a determination of the rate at which the Universe is expanding, a value known as the Hubble Constant. This figure has evolved over time, shrinking from Hubble’s initial estimate of about 500 kilometers (310 miles) per second per megaparsec (a million parsecs, with a parsec being 3.26 light years). At that rate (abbreviated as 500 km/sec/Mpc), the Universe would’ve taken only two billion years to reach its observed size—but by the 1930s, rocks older than that were already being found. Modern evidence suggests that the expansion of the Universe began 13.8 billion years ago, at a point in time dubbed the “Big Bang.” This means that Hubble’s figure was a tad high.

In the mid-1990s, astronomers Brian Schmidt, Saul Perlmutter, and Adam Riess took careful measurements of Type 1a supernovae, which are a “standard candle” in astronomy that can help determine cosmic distances. They found that the supernovae were fainter than expected had they been moving at a constant speed, thus were farther away than expected. From that, the astronomers calculated that instead of remaining constant or slowing due to the gravitational effects of the mass of the Universe, the expansion has been accelerating for about the past five billion years. To account for this acceleration, they proposed “dark energy,” which is an as-yet-unexplained factor that appears to repel the galaxies from each other.

What was until recently the most accurate calculation for the Hubble Constant yet was based on measurement of the Cosmic Microwave Background—the “afterglow” of the Big Bang itself—using data from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and theEuropean Space Agency’s Planck satellite. This yielded a value of 66.5 km/sec/Mpc, with an uncertainty of five to ten percent.

But Riess (who, incidentally, shared the 2011 Nobel Prize in Physics for the discovery of the accelerated expansion) wasn’t done. In a paper to appear in the Astrophysical Journal, he announces that his team (which includes UC Berkeley astronomer and Academy Fellow Alex Filippenko), painstakingly studied 300 Type 1a supernovae and 2400 Cepheid variable stars (another “standard candle” in astronomy) to produce what is the most precise measurement of the Hubble Constant yet, to an uncertainty of only 2.4 percent—a figure of 73.2 kilometers per second /Mpc.

The discrepancy between the new figure and the previous WMAP/Planck calculation is puzzling. Reiss compares the two to a bridge construction project: “You start at two ends, and you expect to meet in the middle if all of your drawings are right and your measurements are right. But now the ends are not quite meeting in the middle and we want to know why.”

Filippenko says, “There is a problem with predictions based on measurements of the Cosmic Microwave Background radiation...Maybe the Universe is tricking us, or our understanding of the Universe isn’t complete.”

Which is a bit of an understatement. —Bing Quock

Images: Jupiter, de Pater, et al., NRAO/AUI/NSF; NASA; Pluto, NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Share This