Scientists have proposed several hypotheses for the climate shift that struck east africa , said peter demenocal , a marine geologist and geochemist at columbia university .
Research by geochemist gabriel filippelli at indiana university-purdue university indianapolis has found that soil in abandoned urban lots claimed by gardeners in industrial cities like baltimore , brooklyn , detroit and indianapolis is sometimes contaminated with lead .
" This means the atmosphere arrived far later than expected . " To confirm that comets contributed to the atmosphere , scientists will need to analyze the krypton and xenon isotope ratios in the cometary samples recently captured by nasa 's stardust mission , says geochemist and lead author greg holland , also at manchester .
The team 's results " suggest that analyses of zircon inclusions can 't be trusted much at all , " adds jonathan patchett , an isotope geochemist at the university of arizona in tucson . " This is really nice work , very strong . "
Two weeks after president barack obama pulled the plug on yucca mountain , the site near las vegas where the federal government has been trying for 22 years to open a repository for nuclear waste , geochemist james l. conca came to washington , d.c. , with an idea in his pocket .
After the eruption , " the world would have been a strangely green place , with simple plants like club mosses , but also lots and lots of dead trees , " said lead study author mark sephton , a geochemist at imperial college london .
So geochemist robert hazen of the carnegie institution of washington in washington , d. c. , and colleagues traced the origins of nearly 3000 common terrestrial minerals -- such as turquoise , azurite , and malachite -- to about a dozen ancient minerals .
A team led by geochemist alberto saal of brown university decided to use a more sensitive method .
由brown大学的地球化学家albertosaal带领的小组决定采用一个更敏感的方法。
Other scientists , including paul knauth , an isotope geochemist at arizona state university , tempe , are more open to retallack 's arguments .
其他科学家包括但佩市亚利桑那州立大学同位素地球化学家鲍尔-克劳斯,则更乐意接受丽塔来克的论点。
Geochemist and lead author zachary sharp of the university of new mexico , albuquerque , explains that the chlorine isotope ratio is a highly reliable indicator of the amount of hydrogen a planetary body contains .