Monday, 6 May 2013

PAN has moved again [UPDATED]

On April 23 I wrote the following about PAN (2009-047A) and its frequent relocations in my post here:

"No doubt it will move again in the future, perhaps in May as December and May are frequently the months the satellite is moved"

I was very right with the "perhaps in May": PAN is on the move again!

Greg Roberts observing from South-Africa noted it missing at its old position on April 29. He recovered it on May 4th near the commercial geostationary Comsat Yamal 404. It is not (yet) clear whether that is its final position, or whether it is still drifting. Greg next initially thought he recovered it near the commercial comsat Yamal 404 on imagery from May 4th, but that turned out to be a mistake: as Mike McCants pointed out, the object in question was in reality the commercial geosat GSAT 8.

Ian Roberts, another South African observer, then located what likely indeed is PAN near Intelsat 12 on May 6th. Greg Roberts then managed to find it in his earlier images of May 4th as well, confirming Ian's observations.

Just goes to show that even the most secret of all satellites cannot escape the inquisitive eyes of a dedicated amateur.

Friday, 3 May 2013

No, fragments of the Tunguska object have not been found - or at least there is no real positive proof of that

The twittersphere, science news sites and mailinglists are abuzz with the story that fragments of the object that caused the famous 30 June 1908 Tunguska explosion have been found.

Most of them link to this post on the MIT Technology Review blog, which bases itself on this manuscript posted to by  a Russian named Andrei Zlobin.

To cut it short: it is highly unlikely the objects in question, which were reportedly retrieved from shoal sediments of the Khusmo river, are fragments of the Tunguska object. The "evidence" provided is wholly unsatisfactory. I am convinced the manuscript will not pass peer review (note that papers posted on are manuscripts: the paper in question hasn't been accepted for publication by any scientific journal yet. And it shouldn't be, in my opinion).

In my opinion the pictured objects look like normal terrestrial iron hydroxide concretions, such as you can find in sandy soils with fluctuating water table and in bogs (and in river sediments that sample such environments). Morphologically they are quite typical for such concretions, especially specimens #3 and #1.

The shell-like character (e.g. #3) is characteristic, as such concretions often form as layers around a core of other material. So I see no reason at all to think these must instead be meteoritic.

In addition, the arxiv paper doesn't give any chemical analysis at all in support of the suggestion these are meteoritic particles. This while such an analysis is the least what you would expect for a claim like this.

The arxiv paper doesn't give any clear chronostratigraphical links between these particles and 1908 (and with this the Tunguska explosion) either. Why should this be particles from the 1908 explosion? What points to that particular origin for these particles? Do they come from sediments that are unambiguously dated to 1908? Zlobin gives no arguments at all.

In other words: this is highly dubious and for now a totally unbelievable story. It is a pitty that many science news websites, starting with the MIT Technology Review but also including are so uncritically disseminating this manuscript.