The Unique Comet Impact Pattern with Reference to Southern Tibet

In the terrestrial planet zone, Comets start outgassing due to solar radiation. This can make comet composition fragile enough to break under the gravitational gradient. Examples like those of Comet Shoemaker-Levy 9 [1] show that it is not unusual for comets to disintegrate due to gravitational gradients. In the event of an impact of such a disintegrated comet on earth, multiple coherent impact craters will be distributed over a large area. The low-density porous composition of the comet will result in the formation of “large flat-floored craters” spread over a large area with a network of faults and fractures as described by Roddy and co-workers (Roddy, 1976;Roddy et al., 1977) [2] [3]. Due to its unusual appearance these impacts patterns are different than rock/metal asteroid impact craters. As a result, these sites are difficult to identify. There are multiple such sites on the planet earth which are under study for impact but due to complex nature of comet impact craters, they have been a conundrum for some time. One such possible site matching the comet impact features can be observed in the southern Tibet between the latitudes of 82°30'E and 90°30'E and 29°N and 33°N. This study indicates that the lakes in this region were formed by the impact of a single disintegrating comet that hit the region. Observation indicates that the lakes are unusually closely aligned and have a steep slope facing circular feature on the eastern side. Fractures and faults connecting these lakes can be observed over entire subject site hinting towards the multiple impact craters. These craters are large flat-floored and spread over a large area. Gravitational anomaly in the lake region along with the presence of Ultra High Pressure (UHP) minerals like cubic Born Nitride, micro-diamond with the inclusion of Platinum Group Elements (PGE), coesite, Stishovite, osbornite and other complex finds in the region support the possibility of impact.

Disintegrated Comet Trail in Southern Tibet

In southern Tibet, there is a series of lakes in the region (82°30'E, 29°N and 90°30'E, 33°N). This study indicates that these lakes were formed by the impact of a single disintegrating comet that hit the region. Observation indicates that the lakes are unusually closely aligned and have a steep slope facing circular feature on the eastern side. Fractures and faults connecting these lakes can be observed over entire subject site hinting towards the multiple impact craters. The terrain is uneven and lakes are partially filled hence in some cases do not look like circular or elliptical. These lakes vary from 1 Km to 65 Km in diameter and are linearly aligned around a single line. Studies of deuterium by Yuan et al. (2011) [1] indicate an abrupt 4‰ increase in δ18O in middle Holocene period around 6000 years ago. The study indicates that the region is rich in diamond, Coesite, Platinum Group Elements (PGE), Stishovite, tektites, and other complex alloys, as would be expected from a high energy impact of an extraterrestrial object. The possibility of the impact as one of the reasons for the diamond in this region was also suggested by Wen-Ji Bai and Qing-Song Fang (2007) [2]. However in absence of definitive evidence they favoured mantle origin. Two possible reasons of absence of impact signature are source of sample and impact pattern. First is the source of the sample which is collected from the river beds of Yarlung-Zangbo Suture Zone of Tibet which is believed to be the origin of this diamond, however it ignores the fact that these rivers get water from lakes which are in the proposed impact zone and the second reason is the impact-pattern spread over close to 800 km which is not expected from the asteroid impact. It will therefore be prudent to test samples from the lake region to understand surface distortion features to confirm the impact. Based on satellite imagery major industrial development supported by road infrastructure in the subject region near lakes and rivers originating from these lakes can be observed hinting towards placer mining activity associated with lakes (craters). Our study suggests that the diamonds, Platinum Group Elements, Stishovite and other alloys harvested from the region should be considered as comet impact diamonds rather than those created in the interior of the earth.