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Cantor B.A.,Malin Space Science Systems | James P.B.,Space Science Institute | Calvin W.M.,University of Nevada, Reno
Icarus | Year: 2010

We used MGS-MOC and MRO-MARCI daily mapping images of the North Polar Region of Mars from 16 August 2005 (Ls=270°) to 21 May 2009 (Ls=270°), covering portions of three consecutive martian years (MY 27-MY 29), to observe the seasonal behavior of the polar ice cap and atmospheric phenomena. The rate of cap regression was similar in MY 28 and MY 29, but was advanced by 3.5° of Ls (~7-8sols) in MY 29. The spatial and temporal behaviors of dust and condensate clouds were similar in the two years and generally in accord with prior years. Dust storms (>100km2) were observed in all seasons, with peak activity occurring at Ls=10-20° from 50°N to 70°N and at Ls=135-140° from 70°N to 90°N. The most active quadrant was 0-90°W in MY 28, shifting to 180-270°W in MY 29. The majority of regional storms in both years developed in longitudes from 10°W to 60°W. During late summer the larger storms obscure the North Polar Region in a cloud of dust that transitions to north polar hood condensate clouds around autumnal equinox.Changes in the distribution of perennial ice deposits, especially in Olympia Planum, were observed between the 2. years, with the MY 29 ice distribution being the most extensive observed to date. Modeling suggests that the small, bright ice patches on the residual cap are not the result of slope or elevation effects. Rather we suggest that they are the result of local meteorological effects on ice deposition. The annual darkening and brightening of peripheral areas of the residual cap around summer solstice can be explained by the sublimation of a brighter frost layer revealing an underlying darker, ice rich layer that itself either sublimes to reveal brighter material below or acts as a cold trap, attracting condensation of water vapor that brightens the surface. An alternative explanation invokes transport and deposition of dust on the surface from the cap interior, and later removal of that dust. The decrease in cap albedo and accompanying increase in near surface atmospheric stability may be related to the annual minimum of polar storm activity near northern summer solstice. © 2010 Elsevier Inc.

James P.B.,Space Science Institute | Thomas P.C.,Cornell University | Malin M.C.,Malin Space Science Systems
Icarus | Year: 2010

We have used Mars Reconnaissance Orbiter data from 2007 and 2009 to compare summer behaviors of the seasonal and residual south polar caps of Mars in those two years. We find that the planet-encircling dust storm that occurred in the first of the two Mars years enhanced the loss of seasonal CO2 deposits relative to the second year but did not have a large effect on the continuing erosion of the pits and mesas within the residual cap materials. This suggests that the increase of bright frost in some regions of the residual cap observed between Mariner 9 and Viking can be accommodated within observed martian weather variability and does not require unknown processes or climate change. © 2010 Elsevier Inc.

Calvin W.M.,University of Nevada, Reno | James P.B.,Space Science Institute | Cantor B.A.,Malin Space Science Systems | Dixon E.M.,University of Nevada, Reno
Icarus | Year: 2015

The MARCI camera on the Mars Reconnaissance Orbiter provides daily synoptic coverage that allows monitoring of seasonal cap retreat and interannual changes that occur between Mars year (MY) and over the northern summer. The northern seasonal cap evolution was observed in MY 29, 30 and 31 (12/2007-04/2012). Observation over multiple Mars years allows us to compare changes between years as well as longer-term evolution of the high albedo deposits at the poles. Significant variability in the early season is noted in all years and the retreating seasonal cap edge is extremely dynamic. Detailed coverage of the entire seasonal and residual ice caps allows a broader view of variations in the high albedo coverage and identifies numerous regions where high albedo areas are changing with time. Large areas of disappearance and reappearance of high albedo features (Gemini Scopuli) are seasonally cyclical, while smaller areas are variable on multi-year time scales (Abalso Mensae and Olympia Planitia). These seasonal and interannual changes directly bear on the surface-atmosphere exchange of dust and volatiles and understanding the current net processes of deposition and erosion of the residual ice deposits. Local and regional variation in high albedo areas reflects an interplay between frost deposition, evolution, and sublimation along with deposition and removal of dust. © 2014 The Authors.

News Article | July 8, 2005
Site: www.techworld.com

Several major Linux distributors will announce a new enterprise GNU/Linux operating system based on Debian in August, according to reports. If true, the move would mean a new level of prominence for Debian, as well as for the Linux Standard Base (LSB), a standard for making different vendors' Linux versions as compatible as possible. Mandriva (formerly MandrakeSoft and Conectiva), Progeny and Turbolinux are to unveil the Debian-based software at LinuxWorld in San Francisco next month, according to eWeek. The three vendors, and possibly others, will use the software as the basis for their server distributions, said the report, citing vendor sources. The software will support Red Hat technology such as RPM package management Mandriva responded that it is indeed working with Progeny and Turbolinux on a core distribution supporting the LSB, as part of its work with the Linux Core Consortium (LCC), and as announced last November. But the company said it is not planning an August release, and couldn't confirm the distribution would be based on Debian. The other vendors did not immediately respond to requests for comment. Mandriva, Progeny and Turbolinux are already working together as the founding members of the LCC, created in November 2004 as a way of backing the LSB's standardisation efforts. In some ways the LCC followed in the footsteps of UnitedLinux, a now-defunct attempt at uniting several vendors around a single distribution. UnitedLinux used the enterprise distribution of Novell's Suse Linux as a basic platform, with other founding members including Conectiva, Turbolinux and the SCO Group. The LCC places more emphasis than UnitedLinux on the LSB, a project designed to keep Linux distributions from fragmenting as Unix did. The group said in November it would create a Linux distribution core based on LSB 2.0, to be used by all group members as the basis for their own distributions, and maintained under a joint development framework. The core was originally planned for the first quarter of this year, but has not yet been released. Greater standardisation in the Linux world would simplify things for sysadmins by reducing differences such as installation procedures and application availability. Software and hardware vendors could also benefit - the LCC plans to allow them to certify for the single core instead of for each individual distribution. The rise of Debian The LCC did not initially specify that Debian would be the basis for their distribution, but such a move would make sense, according to many in the industry. Debian was intended as the LSB's reference distribution when the LSB was initially founded. And Debian has become a platform of choice for new distributions. Commercial distributions Linspire, Xandros, Ubuntu and Progeny are all based on Debian. So are the Linux distributions customised for Munich and Vienna, LiMux and Wienux, and Extremadura in Spain, known as LinEx. Last month's stable release of "Sarge", the latest Debian version, has added to the interest. Debian is not itself a commercial distribution, but is regarded as one of the most technologically advanced Linux versions. Ian Murdock, founder of Debian as well as chairman and chief strategist at Progeny, has said in recent interviews that Mandriva's strategy of acquiring smaller Linux vendors around the world - such as Conectiva and the assets of Lycoris - means the company's shift to a Debian base is practically inevitable.

Daubar I.J.,University of Arizona | McEwen A.S.,University of Arizona | Byrne S.,University of Arizona | Kennedy M.R.,Malin Space Science Systems | Ivanov B.,Russian Academy of Sciences
Icarus | Year: 2013

The discovery of 248 dated impact sites known to have formed within the last few decades allows us to refine the current cratering rate and slope of the production function at Mars. We use a subset of 44 of these new craters that were imaged before and after impact by Mars Reconnaissance Orbiter's Context Camera - a thoroughly searched data set that minimizes biases from variable image resolutions. We find the current impact rate is 1.65×10-6 craters with an effective diameter ≥3.9m/km2/yr, with a differential slope (power-law exponent) of -2.45±0.36. This results in model ages that are factors of three to five below the Hartmann (Hartmann, W.K. [2005]. Icarus 174, 294-320) and Neukum et al. (Neukum, G., Ivanov, B.A., Hartmann, W.K. [2001]. Space Sci. Rev. 96, 55-86)/Ivanov (Ivanov, B.A. [2001]. Space Sci. Rev. 96, 87-104) model production functions where they overlap in diameter. The best-fit production function we measure has a shallower slope than model functions at these sizes, but model function slopes are within the statistical errors. More than half of the impacts in this size range form clusters, which is another reason to use caution when estimating surface ages using craters smaller than ~50m in diameter. © 2013 Elsevier Inc.

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