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News • Mission Update Space Shorts After Kepler, TESS NASA’s Astrophysics Explorer Program has selected the Transiting Exoplanet Survey Satellite (TESS) mission to fly in 2017. TESS will use an array of four telescopes to perform an all-sky survey to discover transiting exoplanets of all sizes in orbit around the nearest and brightest stars in the sky. Its goal is to identify terrestrial planets in the habitable zones of nearby stars that are best suited for extensive follow-up observations and characterization, including with the James Webb Space Telescope. TESS will collect 10 times as much data during its two-year mission as Kepler did during its first two years. Its principal investigator is George Ricker of the Massachusetts Institute of Technology. http://1.usa.gov/12UIonD NICER gets go-ahead The Neutron Star Interior Composition Explorer has been chosen as the second mission for NASA’s Astrophysics Explorer Program. NICER will be placed on the International Space Station and will measure the variability of cosmic X-ray sources, a process called X-ray timing, to explore the exotic states of matter within neutron stars and reveal their interior and surface compositions. The principal investigator is Keith Gendreau of NASA’s Goddard Space Flight Center. http://heasarc.gsfc.nasa.gov/docs/nicer Brightest, longest GRB The highest-energy light ever recorded from a gamma-ray burst was detected by NASA’s Fermi Gamma Ray Space Telescope on 27 April and then by automatically alerted space-based observatories such as Swift. Fermi’s Large Area Telescope recorded a gammaray with an energy of at least 94 GeV and high-energy emission from the burst was detectable for most of a day rather than the usual minutes. It was later seen in optical, infrared and radio wavelengths by ground-based observatories, based on the position from Swift. This burst was about 3.6 billion light-years away, in the nearest 5% of GRBs, and astronomers then looked for the supernova expected to be found within a week or so. http://1.usa.gov/10q2ie7 3.8 Mission update Time runs out for Herschel ESA’s Herschel space observatory stopped working on 29 April after more than three years of operation, when it exhausted its liquid helium coolant. Herschel used the biggest single mirror – 3.5 m diameter – built for a space observatory and observed from far infrared to submillimetre wavelengths. The liquid helium was needed to cool the instrument close to absolute zero; rising instrument temperatures confirmed the end of this phase of the mission. Herschel’s science return is by no means finished, however, as there is plenty to discover within the legacy data. Herschel made more than 35 000 scientific observations, amassing more than 25 000 hours’ worth of science data from about 600 observing programmes. A further 2000 hours of calibration observations also contribute to the rich dataset, which is based at ESA’s European Space Astronomy Centre, near Madrid in Spain. Herschel observes the cool, dark universe, and has been a very effective probe of water and other volatiles in star-forming regions and planetary discs, for example. Now Herschel data have shown a difference in stratospheric water content between the northern and southern hemispheres of Jupiter, attributed to the impact of comet Shoemaker-Levy 9 in July 1994. Water was detected at the time of the impact of comet SL9, but direct proof of its persistence at Jupiter was lacking. ESA’s Infrared Space Observatory found water in the stratosphere in 1997, and its origin became a matter of debate; there is not enough oxygen in the upper atmospheric layers to form Argon argues for atmosphere loss on Mars Isotopes of noble gas argon provide strong support for the idea that Mars has lost much of its atmosphere over time. Measurements of the martian atmosphere using the quadrupole mass spectrometer in the Sample Analysis at Mars instrument (SAM) on Mars Science Laboratory’s Curi- 1: Jupiter’s asymmetrical high-altitude water abundance in pale blue. (ESA/Herschel/T Cavalié et al.; and NASA/ESA/R Beebe NMSU) it there. Other possible sources include local sources on the planet or from rings and satellites of Jupiter or from interplanetary dust. Now an international team led by Thibault Cavalié of the University of Bordeaux/CNRS used the Heterodyne Instrument for the Far Infrared (HIFI) and the Photodetector Array Camera and Spectrometer (PACS) onboard Herschel to map the distribution of water, mapping Jupiter’s stratospheric temperature with the NASA Infrared Telescope Facility (IRTF) at the same time in order to measure temperature independently. They have produced a map of the disc of Jupiter using PACS and a vertical http://bit.ly/10qop41 osity rover found about four times as much 36Ar as 38Ar. This ratio of stable isotopes is significantly lower than that in the solar system as a whole, based on measurements from the Sun and Jupiter, and points to a mechanism that preferentially removes the lighter isotope rather than the heavier one. Loss of atmospheric constituents to space could produce the stable isotope ratios observed. Curiosity’s measurements are more precise than previous estimates taken from the Viking probe in 1976 and from martian meteorites. Erosion of the martian atmosphere by the charged particles of the solar wind was measured in 2004 by the European team using ASPERA-3 on ESA’s Mars Express orbiter. Curiosity’s SAM instrument suite has also picked out volatile compounds in a sample of rocks drilled at the Yellowknife site within Gale Crater. The gases given off when the powder sample was heated – and the temperatures at which they were detected – point towards rocks profile through the stratosphere using HIFI (figure 1). The water is present at low pressures, in the upper parts of the atmosphere, and is more abundant in the southern hemisphere than the northern. The vertical profile indicates supply from off the planet, relatively recently so that it has not had time to mix throughout Jupiter’s layers and remove the asymmetry. While moons, rings and interplanetary dust cannot be entirely ruled out, the majority of the water it likely to have come from the comet impact 19 years ago. Cavalié et al. published the results in Astronomy & Astrophysics. A&G • June 2013 • Vol. 54 News • Mission Update Cassini sees hurricane in Saturn’s hexagon The Cassini spacecraft has taken a close look at a vast storm system within the hexagonal weather pattern at the north pole of Saturn. The storm looks very like a hurricane on Earth, but it is much bigger: the clear central eye of the storm is about 2000 km across – ten times the typical size on Earth – and clouds at the outer edge of the hurricane on Saturn are moving at more than 500 kph – rather faster than on Earth! One difference from terrestrial hurricanes is that this storm is locked into the weather system at the pole, rather than sweeping round the planet as happens on Earth. The existence of this storm poses questions about both Saturn and Earth. Terrestrial hurricanes get their energy from warm ocean water; this system on Saturn does not have a handy warm ocean, although it does use a relatively small amount of water vapour within the hydrogen atmosphere. Understanding how this storm system evolves may shed light on the mechanisms of terrestrial storms. Cassini is a joint project of NASA, ESA and the Italian Space Agency and has been observing Saturn since 2004. Scientists have not seen the north pole so clearly in the past because it is only now emerging from winter. Cassini’s composite infrared spectrometer and visual and infrared mapping spectrometer detected the great hexagonal vortex, but now it is visible. Cassini is also getting better views of the poles because it is following more highly inclined orbits, using Titan’s gravity to change the angle. http://1.usa.gov/13yrn5x containing hydrated minerals, carbonates, perchlorates, sulphates and sulphides and clays. This was the result of the fourth powder sample from one rock (called John Klein by the rover team) and highlights the effectiveness of the powder analysis that Curiosity can perform. http://ssed.gsfc.nasa.gov/sam Super-Earths found around a Sun-like star NASA’s Kepler mission has found a system of five small planets including two “super-Earths” orbiting in the habitable zone of the star, a K-type star slightly smaller than the Sun. If these planets are rocky or water worlds, they are potential targets for the search for extraterrestrial intelligence. Kepler astronomers established that this system comprises five planA&G • June 2013 • Vol. 54 2: A false-colour image of the north polar region of Saturn using filters sensitive to near-infrared light: wavelengths of 890 nm are projected as blue, 728 nm as green, and 752 nm as red. Red indicates low clouds and green indicates high ones. The image was taken from a distance of 419 000 km. (NASA/JPL-Caltech/SSI) ets the size of Earth or a bit bigger on the basis of repeated transit data, reinforced by comparison with other Kepler multiple-planet systems. The outermost planet, Kepler-62f, about 1.4 times the radius of Earth with a period of 267 Earth days, orbits in the habitable zone for a planet with an atmosphere like that of Earth. Kepler-62e, about 1.6 times Earth’s radius and with a period of 122 Earth days, is probably also in the habitable zone so liquid water may exist on its surface, too. But because the Kepler team has only transit data, the masses of these planets remain uncertain and it is not clear whether they are rocky or perhaps water planets. They are also, at 850 light-years distance, too far from Earth for any atmospheric compositions to be determined. This system is an especially significant discovery, however, because it adds to the numbers of known systems including small planets that orbit in their star’s habitable zones. Knowing the distribution of such small planetary systems will help plan further research on them and their characteristics, possibly including those closer to Earth. http://www.seti.org/seti_kepler_62 HARPS-N gives exoplanet mass Astronomers have combined data from the Kepler space telescope with that from the new HARPS-N spectrograph on La Palma to characterize two new exoplanets, adding their mass to determinations of planetary radius and orbital period. HARPS-N is the new high-accuracy spectrograph working in the northern hemisphere, a counterpart to the HARPS instrument at the European Southern Observatory, able to pick out radial velocity variations of less than 1 m s –1. These data complement Kepler’s transit data, as established by work com- bining high-resolution spectroscopy from SOPHIE, an instrument at the Observatoire de Haute-Provence that has been examining exoplanets since 2010. An international team led by G Hébrard (Institut d’Astrophysique de Paris/Observatoire de HauteProvence) has now characterized two Jupiter-sized planets with eccentric orbits smaller than that of Mercury in the solar system, and periods of less than 10 days. KOI-200b is slightly bigger and less massive than Jupiter, orbiting around its star in less than one week. The planet KOI889b is of the size of Jupiter but is 10 times more massive, orbiting around its star in slightly less than 9 days. These two planets have eccentric orbits giving rise to variations in their equilibrium temperature of several hundred degrees over just a few days. Such eccentric orbits are rare for “hot Jupiters”, giant planets orbiting close to their parent stars. http://bit.ly/13hYcEv 3.9