The mitochondrial inner membrane contains a large protein complex that functions in inner membrane organization and formation of membrane contact sites. The complex was variably named the ...mitochondrial contact site complex, mitochondrial inner membrane organizing system, mitochondrial organizing structure, or Mitofilin/Fcj1 complex. To facilitate future studies, we propose to unify the nomenclature and term the complex "mitochondrial contact site and cristae organizing system" and its subunits Mic10 to Mic60.
Long before Galileo published his discoveries about Jupiter, lunar craters, and the Milky Way in the Starry Messenger in 1610, people were fascinated with the planets and stars around them. That ...interest continues today, and scientists are making new discoveries at an astounding rate. Ancient lake beds on Mars, robotic spacecraft missions, and new definitions of planets now dominate the news. How can you take it all in? Start with the new Encyclopedia of the Solar System, Second Edition.This self-contained reference follows the trail blazed by the bestselling first edition. It provides a framework for understanding the origin and evolution of the solar system, historical discoveries, and details about planetary bodies and how they interact—and has jumped light years ahead in terms of new information and visual impact. Offering more than 50% new material, the Encyclopedia includes the latest explorations and observations, hundreds of new color digital images and illustrations, and more than 1, 000 pages. It stands alone as the definitive work in this field, and will serve as a modern messenger of scientific discovery and provide a look into the future of our solar system.· Forty-seven chapters from 75+ eminent authors review fundamental topics as well as new models, theories, and discussions · Each entry is detailed and scientifically rigorous, yet accessible to undergraduate students and amateur astronomers · More than 700 full-color digital images and diagrams from current space missions and observatories amplify the chapters · Thematic chapters provide up-to-date coverage, including a discussion on the new International Astronomical Union (IAU) vote on the definition of a planet · Information is easily accessible with numerous cross-references and a full glossary and index
The peculiar object P/2010 A2 was discovered in January 2010 and given a cometary designation because of the presence of a trail of material, although there was no central condensation or coma. The ...appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized class of main-belt comets. If confirmed, this new object would expand the range in heliocentric distance over which main-belt comets are found. Here we report observations of P/2010 A2 by the Rosetta spacecraft. We conclude that the trail arose from a single event, rather than a period of cometary activity, in agreement with independent results. The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around 10 February 2009.
•Photometry of the S-type Itokawa observed by multi-band filters is examined.•AMICA/Hayabusa successfully observed the opposition surge of the asteroid Itokawa.•Itokawa's single-scattering albedo is ...0.57 ± 0.05, brighter than Eros.•Photometric modeling suggests a high porosity for Itokawa's surface.
We present photometry of the S-type near-Earth asteroid 25143 Itokawa based on both ground-based observations in the UBVRI bands and measurements from the AMICA/Hayabusa spacecraft observations with ul-, b-, v-, w-, x-, and p-filters. Hayabusa observed Itokawa around opposition during the rendezvous, thus providing a unique set of observations of this asteroid. We fit the phase curve measurements with both the Classic Hapke Model (Hapke, 1981, 1984, 1986) and Modern Hapke Model (Hapke, 2002, 2008, 2012a) and thereby extract the physical properties of Itokawa's surface regolith. The single-scattering albedo (0.57 ± 0.05) is larger than that derived for Eros (0.43 ± 0.02), another S-type near-Earth asteroid visited by a spacecraft. Both models indicate a regolith that is forward-scattering in nature. From the hockey stick relationship derived for the single-particle phase function (Hapke, 2012b), both modeling results suggest a regolith comprised of rough surfaced particles with a low density of internal scatterers. Application of the Modern Hapke model derives porosity parameter values from 1 to 1.1, for BVR bands, which corresponds to porosity values between 77–79%. This suggests the surface of Itokawa is very fluffy and the large boulders may be bonded with smaller size particles, typical of the particle sizes observed in Muses Sea. Both models also provide similar geometric albedo values (0.27 ± 0.02) at the V-band wavelength, which are equivalent to Eros’ geometric albedo.
Spectral similarity of unbound asteroid pairs Wolters, Stephen D; Weissman, Paul R; Christou, Apostolis ...
Monthly notices of the Royal Astronomical Society,
04/2014, Letnik:
439, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Infrared (IR) spectroscopy between 0.8 and 2.5 μ has been obtained for both components of three unbound asteroid pairs, using the NASA Infrared Telescope Facility with the SpeX instrument. Pair ...primary (2110) Moore-Sitterly is classified as an S-type following the Bus-DeMeo taxonomy; the classification for secondary (44612) 1999 RP27 is ambiguous: S/Sq/Q/K/L-type. Primary (10484) Hecht and secondary (44645) 1999 RC118 are classified as V-types. IR spectra for Moore-Sitterly and Hecht are each linked with available visual photometry. The classifications for primary (88604) 2001 QH293 and (60546) 2000 EE85 are ambiguous: S/Sq/Q/K/L-type. Subtle spectral differences between them suggest that the primary may have more weathered material on its surface. Dynamical integrations have constrained the ages of formation: 2110-44612 > 782 kyr; 10484-44645 = 348 (+823,−225) kyr; 88604-60546 = 925 (+842,−754) kyr. The spectral similarity of seven complete pairs is ranked in comparison with nearby background asteroids. Two pairs, 17198-229056 and 19289-278067, have significantly different spectra between the components, compared to the similarity of spectra in the background population. The other pairs are closer than typical, supporting an interpretation of each pair's formation from a common parent body.
Structure and density of cometary nuclei WEISSMAN, Paul R.; LOWRY, Stephen C.
Meteoritics & planetary science,
June 2008, Letnik:
43, Številka:
6
Journal Article
Recenzirano
Odprti dostop
— Understanding the nature of the cometary nucleus remains one of the major problems in solar system science. Whipple's (1950) icy conglomerate model has been very successful at explaining a range of ...cometary phenomena, including the source of cometary activity and the nongravitational orbital motion of the nuclei. However, the internal structure of the nuclei is still largely unknown. We review herein the evidence for cometary nuclei as fluffy aggregates or primordial rubble piles, as first proposed by Donn et al. (1985) and Weissman (1986). These models assume that cometary nuclei are weakly bonded aggregations of smaller, icy‐conglomerate planetesimals, possibly held together only by self‐gravity. Evidence for this model comes from studies of the accretion and subsequent evolution of material in the solar nebula, from observations of disrupted comets, and in particular comet Shoemaker‐Levy 9, from measurements of the ensemble rotational properties of observed cometary nuclei, and from recent spacecraft missions to comets. Although the evidence for rubble pile nuclei is growing, the eventual answer to this question will likely not come until we can place a spacecraft in orbit around a cometary nucleus and study it in detail over many months to years. ESA's Rosetta mission, now en route to comet 67P/Churyumov‐Gerasimenko, will provide that opportunity.
This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The ...extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term
near-Sun comets
to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU).
Sunskirters
are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase
sungrazers
to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed
sundivers
. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics.
The petrologic diversity of meteorites demonstrates that planetesimals ranged from unmelted, variably metamorphosed aggregates to fully molten, differentiated bodies. However, partially ...differentiated bodies have not been unambiguously identified in the asteroid belt. New constraints on the density, composition, and morphology of 21 Lutetia from the Rosetta spacecraft indicate that the asteroid's high bulk density exceeds that of most known chondritic meteorite groups, yet its surface properties resemble those of some carbonaceous and enstatite chondrite groups. This indicates that Lutetia likely experienced early compaction processes like metamorphic sintering. It may have also partially differentiated, forming a metallic core overlain by a primitive chondritic crust.
► Lutetia is of sufficient size to be melted and potentially retain its original radial structure. ► Lutetia's surface resembles that of a carbonaceous or enstatite chondrite. ► The asteroid's bulk density equals or exceeds that of all non-CB carbonaceous chondrites. ► Lutetia at least experienced early metamorphic sintering and other compaction processes. ► Lutetia also may be partially differentiated, containing a metallic core overlain by a chondritic crust.
The Large-Grained Dust Coma of 174P/Echeclus Bauer, James M.; Choi, Young-Jun; Weissman, Paul R. ...
Publications of the Astronomical Society of the Pacific,
04/2008, Letnik:
120, Številka:
866
Journal Article
Recenzirano
On 2005 December 30, Y.-J. Choi and P. R. Weissman discovered that the formerly dormant Centaur 2000 EC98 was in strong outburst. Previous observations by P. Rousselot et al. spanning a 3-year period ...indicated a lack of coma down to the27 mag arcsec-2
27
mag
arcsec
-
2
level. We presentSpitzer Space TelescopeMIPS observations of this newly active Centaur—now known as 174P/Echeclus (2000 EC98)—or 60558 Echeclus—taken in 2006 late February. The images show strong signal at both the 24 and 70 μm bands and reveal an extended coma about 2′ in diameter. Analyses yield estimates of the coma signal contribution that are in excess of 90% of the total signal in the 24 μm band. Dust production estimates ranging from1.7–4 × 102 kg s-1
1.7
–
4
×
10
2
kg
s
-
1
are on the order of 30 times that seen in other Centaurs. Simultaneous visible-wavelength observations were also obtained with Palomar Observatory's 200-inch telescope, the 1.8-m Vatican Advanced Technology Telescope, the Bohyunsan Optical Astronomy Observatory (BOAO) 1.8-m telescope, and Table Mountain Observatory's 0.6-m telescope, revealing a coma morphology nearly identical to the mid-IR observations. The grain size distribution derived from the data yields a log particle mass power-law with slope parameterα = -0.87 ± 0.07
α
=
-
0.87
±
0.07
, and is consistent with steady cometary activity, such as that observed during theStardustspacecraft’s encounter at 81P/Wild 2, and not with an impact-driven event, such as that caused by the Deep Impact experiment.
On 2010 January 18-19 and June 28-29, the Wide-field Infrared Survey Explorer (WISE) spacecraft imaged the Rosetta mission target, comet 67P/Churyumov-Gerasimenko. We present a preliminary analysis ...of the images, which provide a characterization of the dust environment at heliocentric distances similar to those planned for the initial spacecraft encounter, but on the outbound leg of its orbit rather than the inbound. Broadband photometry yields low levels of CO sub(2) production at a comet heliocentric distance of 3.32 AU and no detectable production at 4.18 AU. We find that at these heliocentric distances, large dust grains with mean grain diameters on the order of a millimeter or greater dominate the coma and evolve to populate the tail. This is further supported by broadband photometry centered on the nucleus, which yield an estimated differential dust particle size distribution with a power-law relation that is considerably shallower than average. We set a 3sigma upper limit constraint on the albedo of the large-grain dust at < or =, slant0.12. Our best estimate of the nucleus radius (1.82 + or - 0.20 km) and albedo (0.04 + or - 0.01) are in agreement with measurements previously reported in the literature.
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