* Astronomy

How could evidence of a major asteroid impact have been missed when it was in plain sight all along? The telltale signs of a huge impact site were sitting alongside a busy road 8 kilometres north-east of Santa Fe, New Mexico.
Unusual cracks radiating from the tips of cone-shaped structures in rocks along the Santa Fe National Forest Scenic Byway were first spotted by independent geologist Tim McElvain. He called in experts, who identified the projections as shatter cones, distinctive structures that form when shock waves from a high-speed impact fracture the underlying rock.

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Title: EVIDENCE FOR AN IMPACT STRUCTURE IN THE SANGRE DE CRISTO MOUNTAINS NEAR SANTA FE, NEW MEXICO.
Authors: H. E. Newsom, W. E. Elston, B. A. Cohen, E. L. Tegtmeier, M. T.Petersen, A. S. Read, and T. H. McElvain

Shatter cones discovered in 2005 in road cuts on NM 475 in the Sangre de Cristo Mountains equal those of Sudbury and Vredefort in cm-to-m size. Breccias in Proterozoic crystalline basement and fault blocks of Mississippian-Pennsylvanian carbonates are now being examined to determine whether their distribution is compatible with development stages observed in other large impact structures including:
1) Excavation stage - Ejecta blanket, fall-back breccia, in situ breccias of crater wall and floor.
2) Breccia dikes and pseudotachylites injected into the crater wall and floor, subsequent to the shock wave responsible for shatter cones.
3) Landslide blocks and megabreccias (clasts >1 m) from collapse of the crater wall during the enlargement stage.

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