I've read the paper in Terra Nova. If anyone wants a copy, contact me by PM with your email address and I will send you a copy.<br /><br />Some random notes.<br /><br />Lake Cheko lies within a few km downrange of the central point of the blast, well within the devastation zone.<br /><br />The lake is elongated along the inferred flight path of the impactor.<br /><br />The lake is 400 m wide and 500 m long and 50 m deep. It has been modifed by a very shallow south west extension and a delta built up by the stream entering it. Apart from these the lake is conical in depth profile.<br /><br />The lake is developed in alluvial sediments. Seismic, radar and coring shows that the lake fill is very thin and probably young, little more than a veneer, except where the stream entering it has built up a delta. This is contrary to earlier studies.<br /><br />The permafrost is 25 m thick and beneath the permafrost are organic-rich and methane bearing sediments.<br /><br />Radar, seismic, and coring information show the the lake substrate is heavily disturbed. There is a point reflector at the deepest part that may represent indurated material.<br /><br />How might the lake be explained? the paper considers a number of hypotheses including volcanic, karst, thermokarst, fluvial excavation and impact. Volcanic they exclude because the lake is in alluvial sediments and there is no sign of volcanic activity in the region since the Triassic, more than 200 million years ago. Karst is ruled out because of the lack of limestones. They rule out thermokarst because the lake profile, a deep conical lake, is quite different from that of thermokars lakes in the area which are shallow and flat bottomed. the shape and depth of the lake do not seem consistent with fluvial erosion by a nearby river.<br /><br />That leaves impact. Lake Cheko lies almost at the centre of the largest impact event in recent times. It's orientation is consistent with being a crater formed by a large remnant of the presume <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em> Arthur Clarke</p> </div>