As many of you know many of our group’s research activities involving studying samples from asteroids and planetary surfaces that have been delivered to Earth as meteorites. Meteorites are recovered on Earth either as ‘falls’, when they are witnessed falling as fireball events, or recovered as ‘find’ samples recovered from hot and cold deserts by meteorite search teams.
Although meteorites fall evenly across the Earth’s surface, over two thirds (about 35,000) of the world’s total number of collected specimens have been recovered from Antarctica. This is primarily because ice flow dynamics transport meteorites buried at depth in the ice for hundreds of years, up to localised surface regions, known as Meteorite Stranding Zones (MSZs), allowing for efficient recovery and scientific study (read more about the importance of Antarctic meteorites here).
A team of University of Manchester colleagues Geoff Evatt, Michael Coughlan and David Abrahams from the School of Maths and Katherine Joy, Andrew Smedley and Paul Connolly from the School of Earth, Environmental and Atmospheric Sciences have looked into a problem which has long puzzled meteorite hunters recovering samples from Antarctica: fewer iron-rich meteorites have been found in Antarctica compared to anywhere else on Earth.
Using a combination of mathematical modelling and a series of icy lab experiments (we locked Michael in an ice box for a few weeks!) we propose in our new paper that this under-representation of iron-based meteorites might be the result of the Sun’s rays penetrating the clear ice in MSZs during the summer months and warming the iron-rich rocks more than non-metallic rocks.
In the words of lead author Geoff: “The stony meteorites don’t really conduct energy that well. They absorb the heat from the sun, but it takes them a long time to pass the energy down towards the ice below them.But iron meteorites pick up energy from the sun and quickly transmits the energy to the bottom of it, potentially causing melting of the ice underneath the meteorite”. This ice melting process allows the iron-rich meteorites to effectively sink into the upwelling ice, meaning that they don’t easily emerge onto the surface to be spotted by collection teams. This means that there may be a sparse layer of iron-rich meteorites trapped buried at depths of ~50 cm in the Antarctic ice.
Hopefully future teams of meteorite hunters heading down south to the ice to search in Meteorite Standing Zones will be able to identify and recover such scientifically important samples, though new search techniques may need to be developed to allow searchers to peer down through the ice to see what treasures are buried beneath.
The new paper can be read at: G.W. Evatt, M.J. Coughlan, K.H.Joy, A.R.D. Smedley, P.J. Connolly, I.D. Abrahams (2016) A potential hidden layer of meteorites below the ice surface of Antarctica Nature Communications 7, Article number:10679 doi:10.1038/ncomms10679
Find out more about meteorite hunting teams:
- ANSMET http://caslabs.case.edu/ansmet/ – ANSMET programme and see this map of locations of meteorites recovered from the Transantarctic mountains at http://curator.jsc.nasa.gov/antmet/map.cfm . See the previous E&SS blog here about meteorite hunting with the ANSMET programme
- South Korea https://koreamet.kopri.re.kr/ – recently they have been searching with an Italian team in the Frontier Mountains
- Belgium and Japan http://yamato.nipr.ac.jp/ do joint missions to the Yamoto and Asuka icefields area
Also see the NASA ARES meteorite curation site for details of recovered samples and associated science rationale for meteorite recovery and the Smithsonian who help classify the recovered ANSMET samples
The database of classified meteorites can be found at the Meteoritical Bulletin
If you would like to hold a meteorite in your hand then you can head over to the Manchester Museum where they have a great touch table display with lots of hot desert collected samples you can interact. The exhibit has been put together by our friends at Catch a Shooting Star.
Some other news coverage of this story:
Smithsonian magazine Iron Meteorites Play Hide-and-Seek Under Antarctic Ice
BBC Science News Iron meteorites ‘buried in Antarctica’ by the Sun