Desert Expedition Confirms Spectacular Meteorite Impact
ScienceDaily (Sep. 27, 2010) —
A 2008 Google Earth search led to the
discovery of Kamil crater, one of the best-preserved meteorite impact sites
ever found. Earlier this year, a gritty, sand-blown expedition reached the
site deep in the Egyptian desert to collect iron debris and determine the
crater's age and origins.
One day within the last several
thousand years, a rare metallic meteorite travelling over 12 000 km/hour smashed
into Earth's surface near what is today the trackless border region between
Egypt, Sudan and Libya. The impact of the 1.3 m, 10-tonne chunk of iron
generated a fireball and plume that would have been visible over 1000 km away,
and drilled a hole 16 m deep and 45 m wide into the rocky terrain.
Since then, the crater had sat
undisturbed by Earth's geologic and climatic processes, which usually
render all but the very largest terrestrial impact craters invisible. It was
also, as far as is recorded, unseen by humans.
Searching for craters in Google Earth
But that changed in 2008, when the crater was spotted during a Google Earth
study conducted by mineralologist Vincenzo De Michele, then with the Civico
Museo di Storia Naturale in Milan, Italy. He was searching for natural features,
when by chance he saw the rounded impact crater on his PC screen.
De Michele contacted an astrophysicist, Dr Mario Di Martino, at the INAF
(National Institute for Astrophysics) observatory in Turin, who, together with
Dr Luigi Folco, of Siena's Museo Nazionale dell'Antartide, organised an
expedition to the site in February this year.
It took over a year to plan and obtain permissions for the journey; in the
meantime, and in collaboration with Telespazio, e-Geos and the Italian space
agency ASI, the Kamil region was analysed using satellite data and in particular
high-resolution radar images provided by the ASI-operated COSMO-SkyMed satellite
Expedition to the Egyptian desert
The two-week, 40-person expedition
included Egyptian and Italian scientists, as well as numerous local support
workers, and was conducted as part of the 2009 Italian-Egyptian Year of
Science and Technology (EISY). It was also supported with funding by ESA's Space
Situational Awareness (SSA) programme.
Three-day drive to reach Kamil crater
After a tiring, GPS-guided, three-day
drive across the desert in 40°C heat, the team reached the crater.
They collected over 1000 kg of
metallic meteorite fragments, including one 83-kg chunk thought to have
split from the main meteorite body shortly before impact (it was found 200 m
away from the crater). The joint team also conducted a thorough geological and
topographical survey, using ground-penetrating radar to create a 3D digital
terrain model. Geomagnetic and seismic surveys were also carried out.
Ground truth for small-scale impact craters
The researchers were stunned to find that Kamil crater, named after a nearby
rocky outcrop, remains pristine, and must have been created relatively recently.
"This demonstrates that metallic meteorites having a mass on the order of 10
tonnes do not break up in the atmosphere, and instead explode when they reach
the ground and produce a crater," says ESA's Dr Detlef Koschny, Head of Near
Earth Objects segment for the SSA programme.
Kamil crater has become the target of intense interest for geologists,
astrophysicists and even archaeologists.
"We are still determining the geochronology of the impact site, but the
crater is certainly less than ten thousand years old -- and potentially less
than a few thousand. The impact may even
have been observed by humans, and archaeological investigations at nearby
ancient settlements may help fix the date," says Dr Folco.
The data gathered during the expedition will be very useful to ESA's SSA
activities for risk assessment of small asteroids with orbits that approach
Earth, a category to which the Kamil impactor originally belonged.