What did the Earth look like about two billion years ago? New IISc research finds answers

What did Earth look like about two billion years ago, when planet's atmosphere was being oxygenated? By analysing ancient dolomite (carbonate) deposits found in Vempalle, in YSR Kapa district of Andhra Presh, researchers at Indian Institute of Science (IISc) and University of Tennessee have estimated temperature and composition of a shallow, inland sea that most likely existed back in that time, called Palaeoproterozoic era. 

ir findings provide insight into how conditions during that time provided just right ambiance for emergence and bloom of photosyntic algae, Bengaluru-based IISc said in a press release on Monday. 

It also shows how a wealth of data about our planet's past remains hidden inside ancient rocks. 

story of our planet is written in different strata of rocks, explains Prosenjit Ghosh, Professor at Centre for Earth Science (CEaS), IISc, and corresponding author of study published in 'Chemical Geology'. 

Planet Earth hasn't always been this hospitable for life. It has been through different phases of climatic extremes, including periods when carbon dioxide levels were almost too toxic for living creatures, just like our neighbour, Venus. However, various studies of fossils from Palaeoproterozoic era have shown that some life might have existed even under se harsh conditions. 

large amounts of CO2 in atmosphere were absorbed by sea and trapped as carbonates in dolomites, says Yogaraj Banerjee, a former PhD student from CEaS and one of authors. 

(Dolomite) is a direct precipitate from seawater. It provides a signal not only of seawater chemistry but also of seawater temperature, explains Robert Riding, Research Professor at Department of Earth and Planetary Sciences, University of Tennessee, USA, and anor author of study. 

team of researchers collected dolomite samples from chert hard rocks formed by interaction of microbes with seawater  as well as deposits underneath m called dolomitic lime-mud. 

Having first identified strata of rock where dolomitic mud could be found, researchers extracted and transported m back to lab. n, y used a state-of--art technique known as clumped isotope rmometry to analyse m. technique allows scientists to narrow down temperature and composition of deposits by looking at arrangement of carbon and oxygen bonds. 

After two years of intense analysis, team was able to figure out from dolomitic mud that temperature of seawater during its original time period was about 20 degree centigre. 

This is in contrast to previous studies that analysed only chert samples from around same period, and h estimated that temperature was higher, around 50 degree centigre. lower temperature estimate from current study agrees more closely with ory that conditions were ideal for supporting lifeforms. 

During Palaeoproterozoic era, of water present was earlier believed to be only heavy water, containing a specific set of isotopes or forms of hydrogen. However, in current study, team showed that light water regular form of water found even today was also present back n. 

Taken toger, se insights lower seawater temperature and presence of light water strongly support hyposis that conditions around two billion years ago were just right for photosyntic algae to emerge. se algae were mainly responsible for pumping oxygen into atmosphere, and making way for or lifeforms to evolve and populate planet. 

team now plans to search for similar lime-mud deposits in or places around world to gar ditional insights about Palaeoproterozoic era.