The surface age of Sputnik Planum, Pluto, must be less than 10 million years

Data from the New Horizons mission to Pluto show no craters on Sputnik Planum down to the detection limit (2 km for low resolution data, 625 m for high resolution data). The number of small Kuiper Belt Objects that should be impacting Pluto is known to some degree from various astronomical surveys. We combine these geological and telescopic observations to make an order of magnitude estimate that the surface age of Sputnik Planum must be less than 10 million years. This maximum surface age is surprisingly young and implies that this area of Pluto must be undergoing active resurfacing, presumably through some cryo-geophysical process. We discuss three possible resurfacing mechanisms and the implications of each one for Pluto's physical properties.Comment: 6 pages; 1 figure; in press at PLOS ON

Comments on the commercialization of expendable launch vehicles

The President's national space policy encourages private sector investment and involvement in civil space activities. Last November, the President designated the Department of Transportation as lead agency for the commercialization of expendable launch vehicles. This presents a substantial challenge to the United States Government, since the guidelines and requirements that are set now will have great influence on whether American firms can become a viable competitive industry in the world launch market. There is a dual need to protect public safety and free the private sector launch industry from needless regulatory barriers so that it can grow and prosper

Space-Based Thermal Infrared Studies of Asteroids

Large-area surveys operating at mid-infrared wavelengths have proven to be a valuable means of discovering and characterizing minor planets. Through the use of radiometric models, it is possible to derive physical properties such as diameters, albedos, and thermal inertia for large numbers of objects. Modern detector array technology has resulted in a significant improvement in spatial resolution and sensitivity compared with previous generations of space-based infrared telescopes, giving rise to a commensurate increase in the number of objects that have been observed at these wavelengths. Space-based infrared surveys of asteroids therefore offer an effective means of rapidly gathering information about small body populations' orbital and physical properties. The AKARI, WISE/NEOWISE, Spitzer, and Herschel missions have significantly increased the number of minor planets with well-determined diameters and albedos.Comment: Chapter for Asteroids IV book (accepted for publication

The Incidence of Debris Disks at 24 {\mu}m and 670 Myr

We use Spitzer Space Telescope 24 {\mu}m data to search for debris disks among 122 AFGKM stars from the \sim 670 Myr clusters Hyades, Coma Ber, and Praesepe, utilizing a number of advances in data reduction and determining the intrinsic colors of main sequence stars. For our sample, the 1{\sigma} dispersion about the main sequence V-K, K-[24] locus is approximately 3.1%. We identify seven debris disks at 10% or more (\geq 3{\sigma} confidence level) above the expected K-[24] for purely photospheric emission. The incidence of excesses of 10% or greater in our sample at this age is 5.7 +3.1/-1.7%. Combining with results from the literature, the rate is 7.8 +4.2/-2.1% for early- type (B9 - F4) stars and 2.7 +3.3/-1.7% for solar-like (F5 - K9) stars. Our primary sample has strict criteria for inclusion to allow comparison with other work; when we relax these criteria, three additional debris disks are detected. They are all around stars of solar-like type and hence reinforce our conclusion that disks around such stars are still relatively common at 670 Myr and are similar to the rate around early-type stars. The apparently small difference in decay rates between early-type and solar-like stars is inconsistent with the first order theoretical predictions that the later type stellar disks would decay an order of magnitude more quickly than the earlier type ones.Comment: 26 pages, 3 figures, accepted for publication in Ap

The Relationship between Site Contamination and Native Plant Success in Butte, MT: Implications for Future Restoration

Interest in ecological restoration of mining impacted areas, as opposed to traditional reclamation practices, has been increasing in recent years. Holistic ecological restoration is preferable to traditional reclamation practices as it provides better ecological function, biodiversity, and human enjoyment. However, legacy effects of mining, such as metals contamination and poor growing substrates, has hampered restoration efforts and further, there is little research on primary succession of these novel ecosystems. There is also scant information on many native plant species responses to contamination. This study focuses on developing plant-contaminant relationships to guide restoration planting decisions. We look at Butte, MT, an area severely impacted by mining operations for over 100 years. Many plant species have spontaneously colonized this contaminated environment, and we show that low pH and elevated levels of Zn are limiting factors to plant growth and we present new information showing Cu as a driver for exotic species invasion. Many native plant species such as Agrostis scabra, Oryzopsis hymenoides, and Mentzelia laevicaulis, are highly tolerant to a range of contaminants. This new information can be used to guide future ecological restoration projects to produce more desirable outcomes while also serving to protect human health. More research, however, should be done to investigate contaminant relationships with additional soil parameters and how they affect native plant colonization

The Comorbidity of Eating Disorders and Substance Abuse in Adolescents and Young Adults

Eating disorders and substance abuse are both predominant issues that the United States faces today especially within the adolescent populations. Together, they can have serious consequences. And unfortunately many individuals suffering from an eating disorder or substance abuse problem develop its counterpart at some point in their lifetime. The National Center on Addiction and Substance Abuse (CASA) at Columbia University found in their three year study (2003) that “individuals with eating disorders are up to five times likelier to abuse alcohol or illicit drugs and those to abuse alcohol or illicit drugs and those who abuse alcohol or illicit drugs are up to 11 times likelier to have eating disorders”. This paper explores the comorbidity of eating disorders and substance abuse among the adolescent population in America. It will first look very briefly at each disorder separately, and then review the literature and studies that look at the overlap between the two. By comparing common personal, social and societal risks that are shared by those affected by eating disorders and substance abuse, this paper will attempt to explain the co-occurrence between the two disorders and demonstrate the causal linkages. Finally, I will bring my own thoughts, reactions, critiques and areas where I see need for further exploration