|
|
| Reconnection and waves: a review with a perspective |
| This review is intended to help prepare a new stage of wave studies in the context of magnetic reconnection. Various results that have accumulated would not let the two-dimensional, steady and laminar magnetic reconnection to remain as the standard model. Emphasis on three-dimensional, temporally varying, and turbulent effects is growing and this fact tells that the effects of waves in various frequency ranges deserve further attention in the context of magnetic reconnection. In this review, by setting a perspective, selected recent topics are reviewed and the ways in which these can be viewed as the stepping stones towards a new research horizon of magnetic reconnection are discussed. |
| Publication date: 27 Jul 2011 |
|
|
| PLATO Definition Study Report (Red Book) |
| Reference: ESA/SRE(2011)13
This report, the so-called Red Book, describes the outcome of the mission definition study (Phase A) for the PLATO mission. PLATO is a medium-size (M-class) mission of the ESA Cosmic Vision 2015-2025 programme, and competes for one of the two launch slots foreseen in 2017 and 2018. |
| Publication date: 25 Jul 2011 |
|
|
| Solar Orbiter definition study report (Red Book) |
| Reference: ESA/SRE(2011)14
This report, the so-called Red Book, presents an overview of the Solar Orbiter mission in its present state of advanced definition. Solar Orbiter is a medium-size (M-class) mission of the ESA Cosmic Vision 2015-2025 programme, and competes for one of the two launch slots foreseen in 2017 and 2018. |
| Publication date: 25 Jul 2011 |
|
|
| EChO External Final Presentation of the CDF study |
Summary of the study performed at ESA's Concurrent Design Facility (CDF), with the goals to:
- Assess the technical feasibility of the ECHO mission proposal
- Design an example mission compatible with achieving the science goals
|
| Publication date: 22 Jul 2011 |
|
|
| MarcoPolo-R near earth asteroid sample return mission |
Made available online before print publication MarcoPolo-R is a sample return mission to a primitive Near-Earth Asteroid (NEA) proposed in collaboration with NASA. It will rendezvous with a primitive NEA, scientifically characterize it at multiple scales, and return a unique sample to Earth unaltered by the atmospheric entry process or terrestrial weathering. MarcoPolo-R will return bulk samples (up to 2 kg) from an organic-rich binary asteroid to Earth for laboratory analyses, allowing us to: explore the origin of planetary materials and initial stages of habitable planet formation; identify and characterize the organics and volatiles in a primitive asteroid; understand the unique geomorphology, dynamics and evolution of a binary NEA. This project is based on the previous Marco Polo mission study, which was selected for the Assessment Phase of the first round of Cosmic Vision. Its scientific rationale was highly ranked by ESA committees and it was not selected only because the estimated cost was higher than the allotted amount for an M class mission. The cost of MarcoPolo-R will be reduced to within the ESA medium mission budget by collaboration with APL (John Hopkins University) and JPL in the NASA program for coordination with ESA's Cosmic Vision Call. The baseline target is a binary asteroid (175706) 1996 FG3, which offers a very efficient operational and technical mission profile. A binary target also provides enhanced science return. The choice of this target will allow new investigations to be performed more easily than at a single object, and also enables investigations of the fascinating geology and geophysics of asteroids that are impossible at a single object. Several launch windows have been identified in the time-span 2020-2024.
- The remainder of the abstract is truncated - |
| Publication date: 20 Jul 2011 |
|
|
| Direct detection of the Enceladus water torus with Herschel |
| Cryovolcanic activity near the south pole of Saturn's moon Enceladus produces plumes of H2O-dominated gases and ice particles, which escape and populate a torus-shaped cloud. Using submillimeter spectroscopy with Herschel, we report the direct detection of the Enceladus water vapor torus in four rotational lines of water at 557, 987, 1113, and 1670 GHz, and probe its physical conditions and structure. We determine line-of-sight H2O column densities of ~4 × 1013 cm-2 near the equatorial plane, with a ~50 000 km vertical scale height. The water torus appears to be rotationally cold (e.g. an excitation temperature of 16 K is measured for the 1113 GHz line) but dynamically excited, with non-Keplerian dispersion velocities of ~2 kms-1, and appears to be largely shaped by molecular collisions. From estimates of the influx rates of torus material into Saturn and Titan, we infer that Enceladus' activity is likely to be the ultimate source of water in the upper atmosphere of Saturn, but not in Titan's. |
| Publication date: 14 Jul 2011 |
|
|
| A giant thunderstorm on Saturn |
| Lightning discharges in Saturn's atmosphere emit radio waves with intensities about 10 000 times stronger than those of their terrestrial counterparts. These radio waves are the characteristic features of lightning from thunderstorms on Saturn, which last for days to months. Convective storms about 2000 kilometres in size have been observed in recent years at planetocentric latitude 35° south (corresponding to a planetographic latitude of 41° south). Here we report observations of a giant thunderstorm at planetocentric latitude 35° north that reached a latitudinal extension of 10 000 kilometres - comparable in size to a 'Great White Spot' - about three weeks after it started in early December 2010. The visible plume consists of high-altitude clouds that overshoot the outermost ammonia cloud layer owing to strong vertical convection, as is typical for thunderstorms. The flash rates of this storm are about an order of magnitude higher than previous ones, and peak rates larger than ten per second were recorded. This main storm developed an elongated eastward tail with additional but weaker storm cells that wrapped around the whole planet by February 2011. Unlike storms on Earth, the total power of this storm is comparable to Saturn's total emitted power. The appearance of such storms in the northern hemisphere could be related to the change of seasons, given that Saturn experienced vernal equinox in August 2009. |
| Publication date: 07 Jul 2011 |
|
|
| Deep winds beneath Saturn's upper clouds from a seasonal long-lived planetary-scale storm |
| Convective storms occur regularly in Saturn's atmosphere. Huge storms known as Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (29.5 Earth years). Current models propose that the outbreak of a Great White Spot is due to moist convection induced by water. However, the generation of the global disturbance and its effect on Saturn's permanent winds have hitherto been unconstrained by data, because there was insufficient spatial resolution and temporal sampling to infer the dynamics of Saturn's weather layer (the layer in the troposphere where the cloud forms). Theoretically, it has been suggested that this phenomenon is seasonally controlled. Here we report observations of a storm at northern latitudes in the peak of a weak westward jet during the beginning of northern springtime, in accord with the seasonal cycle but earlier than expected. The storm head moved faster than the jet, was active during the two-month observation period, and triggered a planetary-scale disturbance that circled Saturn but did not significantly alter the ambient zonal winds. Numerical simulations of the phenomenon show that, as on Jupiter, Saturn's winds extend without decay deep down into the weather layer, at least to the water-cloud base at pressures of 10-12 bar, which is much deeper than solar radiation penetrates. |
| Publication date: 07 Jul 2011 |
|
|
| Extended magnetic reconnection across the dayside magnetopause |
| The extent of where magnetic reconnection (MR), the dominant process responsible for energy and plasma transport into the magnetosphere, operates across Earth's dayside magnetopause has previously been only indirectly shown by observations. We report the first direct evidence of X-line structure resulting from the operation of MR at each of two widely separated locations along the tilted, subsolar line of maximum current on Earth's magnetopause, confirming the operation of MR at two or more sites across the extended region where MR is expected to occur. The evidence results from in-situ observations of the associated ion and electron plasma distributions, present within each magnetic X-line structure, taken by two spacecraft passing through the active MR regions simultaneously. |
| Publication date: 06 Jul 2011 |
|
|
| Fluid dynamics of stellar jets in real time: Third epoch Hubble Space Telescope images of HH 1, HH 34, and HH 47 |
| We present new, third-epoch Hubble Space Telescope H-alpha and [S II] images of three Herbig-Haro (HH) jets (HH 1&2, HH 34, and HH 47) and compare the new images with those from previous epochs. The high spatial resolution, coupled with a time series whose cadence is of order both the hydrodynamic and radiative cooling timescales of the flow, allows us to follow the hydrodynamic/magnetohydrodynamic evolution of an astrophysical plasma system in which ionization and radiative cooling play significant roles. Cooling zones behind the shocks are resolved, so it is possible to identify which way material flows through a given shock wave. The images show that heterogeneity is paramount in these jets, with clumps dominating the morphologies of both bow shocks and their Mach disks. This clumpiness exists on scales smaller than the jet widths and determines the behavior of many of the features in the jets. Evidence also exists for considerable shear as jets interact with their surrounding molecular clouds, and in several cases we observe shock waves as they form and fade where material emerges from the source and as it proceeds along the beam of the jet. Fine structure within two extended bow shocks may result from Mach stems that form at the intersection points of oblique shocks within these clumpy objects. Taken together, these observations represent the most significant foray thus far into the time domain for stellar jets, and comprise one of the richest data sets in existence for comparing the behavior of a complex astrophysical plasma flow with numerical simulations and laboratory experiments. |
| Publication date: 01 Jul 2011 |
|
|
| IJA special issue: Astrobiology field research in Moon/Mars analogue environments |
The International Journal of Astrobiology is a peer-reviewed forum, covering cosmic prebiotic chemistry, planetary evolution, the search for planetary systems and habitable zones, extremophile biology and experimental simulation of extraterrestrial environments, Mars as an abode of life, life detection in our solar system and beyond, the search for extraterrestrial intelligence, the history of the science of astrobiology, as well as societal and educational aspects of astrobiology.
This special issue is devoted to 'Astrobiology field research in Moon/Mars analogue environments' (Editors: BH Foing, C. Stoker, P. Ehrenfreund).
Abstract: Extreme environments on Earth often provide similar terrain conditions to landing/operation sites on the Moon and Mars. Several field campaigns (EuroGeoMars2009 and DOMMEX/ILEWG EuroMoonMars from November 2009 to March 2010) were conducted at the Mars Desert Research Station (MDRS) in Utah. Some of the key astrobiology results are presented in this special issue on 'Astrobiology field research in Moon/Mars analogue environments' relevant to investigate the link between geology, minerals, organics and biota. Preliminary results from a multidisciplinary field campaign at Rio Tinto in Spain are presented. |
| Publication date: 01 Jul 2011 |
|
|
