On March 6 we, at Astroseti.org, published a translation into Spanish about the discovery of Kebira impact crater a 31km diameter structure in Egypt, in the border with Libya, by investigators of Boston University.

Two days later by using Google Earth program I decided to check how this crater looked like, as I knew image quality can vary from one place to another. I thought that logically the silhoute would be hard to appreciate and that would be the reason it took so much time to discover, but following the article guidelines I went directlt to Egypt/Libya border and in less than a minute I perfectly saw the structure.

Kebira as seen from 30km high distance

Suddenly the questions came to me. No one saw this before? How can a 31 km diameter structure not be noticed? So I decided to explore around for a while to check for similar structures.

Just passed the Libyan border entering Chad at 121 miles "flying" high when another circular structure appeared in my screen. A closer look was showing, apparently, a typical impact structure, not volcanic. Of course, finding an impact crater has no merit if it is an already known one, so I had to check and visited the Canadian Brunswick University impact crater database, in Canada, and none of the listed matched my discovery.

The first crater as seen from 20km distance

After a while I decided to "take off" but a few seconds later another suspicious structure just 50km away catched my attention. I went closer and found that my first impression, again, was that it was another impact structure. Once again it was not in the Brunswick University database. It could not be so easy! Was I suffering such excitement that I was seeing impact craters everywhere ?

I searched for more information in the web and found http://www.impact-structures.com curated by two geologists, Kord Ernston of Würzsburg University, and Fernando Claudín, member of Barcelona Museum of Geology, and they were linking to a more comprehensive and updated database. I sent them the images waiting for comments.

Fernando Claudín answer was quite fast. "Circularity doesn't mean anything by itself for identifying an impact structure", he said, "but in the first structure the external ring has layers inclined outwards, and the internal ring has a central elevation. It doesn't look volcanic"

About the second crater he said "not as pronunciated as the first one, but you can appreciate two rings, external and internal, with some paths (and that's good because it means outcrops). The central zone seems collapsed, limited by internal ring"

Confirmation is basically a finantial problem : "it is necessary do some fieldwork with geologists to check if there are breccia, impact metamorfism, etc."

View of second crater from 5000 meters distance

The best for my emotional stability was -without doubt- that he said "it doesn't seem you have the impact discoverer fever. There's enough base to investigate".

So we have two craters that look like being caused by asteroid impacts, but they need a visit to have confirmation.

Both craters are quite close

There should be a mistake somewhere. Even when I was checking point by point I could still not believe I was the first one to see those two structures, so I searched for more information on impact craters in Chad. Google showed me some results about Aorounga, a crater that obviously was already in the known impacts database, but there was a link explaining how Adriana Ocampo, a JPL's geologist had detected other impact craters close to Aorounga by using radar satellite images. But she also needed to confirm the discovery. Was it possible that Adriana's impacts and my impacts were part of the same chain of impacts? Once again I opened Google Earth and traveled to the Aorounga area, high enough to have both groups of craters in the same screen. Distance was 300 km but ... all of them were in line !

I wanted to have more confirmations before publishing, because I didn't want to something that later could became a fiasco. Fernando Claudín wanted Kord Ernstson to give his own opinion so I waited (im)patiently until his mail arrived : "Congratulations ! The structures you discovered in fact look very promising". Then he continued "Having two more craters in Aurunga line is fantastic"", something similar to the impact chain they are studying in Azuara, Spain, between Teruel and Zaragoza.

Finally I received a mail from Jason Hines, Data Manager of the University of Brunswick Impact Structure Database. "It does appear as though you have found possible impact structures", he says but insists "sampling of the site for impact features is the best method to confirm a impact origin".

The story still continues. Right now I'm still waiting for answers from the from David Morrison (curator of NASA's http://impact.nasa.gov) and Adriana Ocampo, who found this discovery interesting enough to confirm her theory about Aorounga if all craters have the same datation.

But the most important thing is, probably, that using a free distributed software ( Google Earth, but I'm also using NASA World Wind) anyone can search for similar structures. Probably I was very lucky, as after this success I spent many hours searching for more without results.

Anyway, if you have decided to search for impact structures, avoid confusing them with volcanos, then check all available known and candidate impact databases and then, and only then : Contact your geologist !!

Good hunt!