In Arthur C. Clarke's novel "2001: A Space Odyssey," astronaut David Bowman exclaims, "My God, it's full of stars!" before he gets pulled into an alien-built wormhole in space. When the Hubble Space Telescope made its deepest views of the universe, astronomers might have well exclaimed: "My God, it's full of galaxies!" The Hubble Ultra Deep Field, for example, revealed 10,000 galaxies of various shapes, sizes, colors, and ages, all within an area roughly one-tenth the diameter of the full moon. What's mind-blowing is that these myriad galaxies, though plentiful, may represent merely 10 percent of the universe's total galaxy population. That's according to estimates from a new study of Hubble's deep-field surveys. The study's authors came to the staggering conclusion that at least 10 times more galaxies exist in the observable universe than astronomers thought.
NASA rethinks approach to Mars exploration
Nature 538, 7624 (2016). http://www.nature.com/doifinder/10.1038/nature.2016.20758
Author: Alexandra Witze
Agency looks to time-allocation model in an era of shifting commercial and international interests.
Planetary science: Moon churn
Nature 538, 7624 (2016). doi:10.1038/538177a
Author: Andrew Mitchinson
The Moon's surface is being mapped by NASA's Lunar Reconnaissance Orbiter spacecraft, to aid planning for future missions. On page 215, Speyerer et al. report how images taken by the orbiter's camera have been used to quantify the current rate at which lunar
History: Einstein the statesman
Nature 538, 7624 (2016). doi:10.1038/538170a
Author: Nancy Thorndike Greenspan
Nancy Thorndike Greenspan enjoys a study of the physicist as engaged public figure.
Quantifying crater production and regolith overturn on the Moon with temporal imaging
Nature 538, 7624 (2016). doi:10.1038/nature19829
Authors: Emerson J. Speyerer, Reinhold Z. Povilaitis, Mark S. Robinson, Peter C. Thomas & Robert V. Wagner
Random bombardment by comets, asteroids and associated fragments form and alter the lunar regolith and other rocky surfaces. The accumulation of impact craters over time is of fundamental use in evaluating the relative ages of geologic units. Crater counts and radiometric ages from returned samples provide constraints with which to derive absolute model ages for unsampled units on the Moon and other Solar System objects. However, although studies of existing craters and returned samples offer insight into the process of crater formation and the past cratering rate, questions still remain about the present rate of crater production, the effect of early-stage jetting during impacts and the influence that distal ejecta have on the regolith. Here we use Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) temporal (‘before and after’) image pairs to quantify the contemporary rate of crater production on the Moon, to reveal previously unknown details of impact-induced jetting, and to identify a secondary impact process that is rapidly churning the regolith. From this temporal dataset, we detected 222 new impact craters and found 33 per cent more craters (with diameters of at least ten metres) than predicted by the standard Neukum production and chronology functions for the Moon. We identified broad reflectance zones associated with the new craters that we interpret as evidence of a surface-bound jetting process. We also observe a secondary cratering process that we estimate churns the top two centimetres of regolith on a timescale of 81,000 years—more than a hundred times faster than previous models estimated from meteoritic impacts (ten million years).
Planetary science: Ocean on another of Saturn's moons
Nature 538, 7624 (2016). doi:10.1038/538143f
Like its neighbours Titan and Enceladus, Saturn's moon Dione may harbour an ocean beneath its icy surface.Mikael Beuthe and his colleagues at the Royal Observatory of Belgium in Brussels studied data collected from Enceladus and Dione by NASA's Cassini spacecraft. They looked for small
Astronomy: Strange fading star probed
Nature 538, 7624 (2016). doi:10.1038/538143c
A star seems to have been dimming for years, possibly because of a cloud of material obscuring it from view.Benjamin Montet at the California Institute of Technology and Joshua Simon at the Carnegie Observatories, both in Pasadena, used instruments on NASA's Kepler spacecraft to