Since a few years there is evidence of a dual meteorite crater at the bottom of Lake Chiemsee (Fig. 4) in the Chiemgau meteorite crater strewn field. The search for a suspected impact into the lake was originally based on reports of fishermen about unusual sharp-edged large stones at the lake bottom that had damaged their fishnets. Such stones are in fact foreign matter in the lake. A general echo sounder campaign, followed by a detailed survey veritably revealed a peculiar structure, likewise a foreign element in the lake, with all evidence of a rimmed doublet crater (Fig.1).
Fig. 1. The proposed meteorite doublet crater at the bottom of Lake Chiemsee from detailed sonar echo sounder measurements. Meter scale indicates water depth.
The similarity to meteoritic dual craters on Mars is striking (Fig. 2). From the Mars image it is evident that the doublet structure formed on synchronous impact of twin projectiles.
Fig. 2. Meteoritic dual craters on Mars (image source NASA) and a counterpart at the bottom of Lake Chiemsee: a remarkable similarity. The more diffuse contours of the Lake Chiemsee craters is not surprising because of the impact into water and a loosely bound and water-saturated sedimentary target below.
Fig. 3. Experimental hypervelocity twin impact into aluminium with the formation of a dual crater (image source NASA) similar to the Chiemgau impact craters at the bottom of Lake Chiemsee.
Fig. 4. Location map for the Lake Chiemsee in southeast Bavaria hiding the probable meteorite doublet crater.