TY  - JOUR
A1  - Jewitt, David
A1  - Weaver, Harold
A1  - Mutchler, Max
A1  - Larson, Stephen
A1  - Agarwal, Jessica
T1  - Hubble space telescope observations of main-belt comet (596) scheila
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - We present Hubble Space Telescope Observations of (596) Scheila during its recent dust outburst. The nucleus remained point-like with absolute magnitude H(V) = 8.85 +/- 0.02 in our data, equal to the pre-outburst value, with no secondary fragments of diameter >= 100m (for assumed albedos 0.04). We find a coma having a peak scattering cross section similar to 2.2x10(4) km(2), corresponding to a mass in micron-sized particles of similar to 4x10(7) kg. The particles are deflected by solar radiation pressure on projected spatial scales similar to 2x10(4) km, in the sunward direction, and swept from the vicinity of the nucleus on timescales of weeks. The coma fades by similar to 30% between observations on UT 2010 December 27 and 2011 January 4. The observed mass loss is inconsistent with an origin either by rotational instability of the nucleus or by electrostatic ejection of regolith charged by sunlight. Dust ejection could be caused by the sudden but unexplained exposure of buried ice. However, the data are most simply explained by the impact, at similar to 5 km s(-1), of a previously unknown asteroid similar to 35m in diameter.
KW  - comets: general
KW  - comets: individual ((596) Scheila)
KW  - minor planets, asteroids: general
Y1  - 2011
U6  - https://doi.org/10.1088/2041-8205/733/1/L4
SN  - 2041-8205
VL  - 733
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Barnett, Ross
A1  - Westbury, Michael V.
A1  - Sandoval-Velasco, Marcela
A1  - Vieira, Filipe Garrett
A1  - Jeon, Sungwon
A1  - Zazula, Grant
A1  - Martin, Michael D.
A1  - Ho, Simon Y. W.
A1  - Mather, Niklas
A1  - Gopalakrishnan, Shyam
A1  - Ramos-Madrigal, Jazmin
A1  - de Manuel, Marc
A1  - Zepeda-Mendoza, M. Lisandra
A1  - Antunes, Agostinho
A1  - Baez, Aldo Carmona
A1  - De Cahsan, Binia
A1  - Larson, Greger
A1  - O'Brien, Stephen J.
A1  - Eizirik, Eduardo
A1  - Johnson, Warren E.
A1  - Koepfli, Klaus-Peter
A1  - Wilting, Andreas
A1  - Fickel, Jörns
A1  - Dalen, Love
A1  - Lorenzen, Eline D.
A1  - Marques-Bonet, Tomas
A1  - Hansen, Anders J.
A1  - Zhang, Guojie
A1  - Bhak, Jong
A1  - Yamaguchi, Nobuyuki
A1  - Gilbert, M. Thomas P.
T1  - Genomic adaptations and evolutionary history of the extinct scimitar-toothed cat
BT  - Homotherium latidens
JF  - Current biology
N2  - Homotherium was a genus of large-bodied scimitar-toothed cats, morphologically distinct from any extant felid species, that went extinct at the end of the Pleistocene [1-4]. They possessed large, saber-form serrated canine teeth, powerful forelimbs, a sloping back, and an enlarged optic bulb, all of which were key characteristics for predation on Pleistocene megafauna [5]. Previous mitochondrial DNA phylogenies suggested that it was a highly divergent sister lineage to all extant cat species [6-8]. However, mitochondrial phylogenies can be misled by hybridization [9], incomplete lineage sorting (ILS), or sex-biased dispersal patterns [10], which might be especially relevant for Homotherium since widespread mito-nuclear discrepancies have been uncovered in modern cats [10]. To examine the evolutionary history of Homotherium, we generated a -7x nuclear genome and a similar to 38x exome from H. latidens using shotgun and target-capture sequencing approaches. Phylogenetic analyses reveal Homotherium as highly divergent (similar to 22.5 Ma) from living cat species, with no detectable signs of gene flow. Comparative genomic analyses found signatures of positive selection in several genes, including those involved in vision, cognitive function, and energy consumption, putatively consistent with diurnal activity, well-developed social behavior, and cursorial hunting [5]. Finally, we uncover relatively high levels of genetic diversity, suggesting that Homotherium may have been more abundant than the limited fossil record suggests [3, 4, 11-14]. Our findings complement and extend previous inferences from both the fossil record and initial molecular studies, enhancing our understanding of the evolution and ecology of this remarkable lineage.
Y1  - 2020
U6  - https://doi.org/10.1016/j.cub.2020.09.051
SN  - 0960-9822
SN  - 1879-0445
VL  - 30
IS  - 24
PB  - Cell Press
CY  - Cambridge
ER  -