My August 2011, Science news roundup: An underground river flowing over two miles beneath the Amazon River has been detected; ancient microbe fossils may have been found in a 3.46 billion year old Australian sandstone bed; a fossil of the earliest placental mammal ancestor has been found in China; a dinosaur era mass extinction of marine life has been attributed to a massive methane gas “burp”
A subterranean river beneath the Amazon?
This past week, scientists from Brazil’s National Observatory detected what appears to be a massive, underground river — named Rio Hamza (after Valiya Hamza, the leader of the expedition) — flowing 4000 meters (13, 000 ft.) beneath the Amazon River. The slower moving, underground river is at least as long as the 6,000 km (3,700 mile) Amazon but is much wider (ranging in width from 200 to 400 km (while the ground level river ranges between 1 and 100 km in width).
The Amazon is the second longest river in the world with an average flow rate of 1,300,000 cubic meters per second. The newly discovered, subterranean Rio Hamza has a much slower flow rate of about 4,000 cubic meters per second since it must travel through densely packed sediment and rock. The underground river, which also flows from west to east, is thought to be fed by drainage from the Amazon. Upward seepage from the river may be the reason why the mouth of the Amazon maintains its low salinity.
The river was detected from examining thermal measurements from over 200 drilling sites left by Brazilian oil giant Petrobras four decades ago. The scientist estimate that it will take three or more years to fully confirm the river’s existence. Source: ‘Subterranean’ Amazon River Reportedly Discovered
Ancient, bacterium-like fossils found in Australian sandstone – world’s oldest?
Paleobiologists claim that eleven varieties of a filamentous microbe (eight of which were previously unknown) with their cell structures preserved were discovered in sandstone at the base of the Strelley Pool rock formation in Western Australia.
Identification of such microfossils is difficult and controversial, as some natural processes can mimic the structure of once-living organisms. But paleobiologists, led by Martin D. Brasier (Univ. of Oxford), claim that their new dating technique points to a biological entity.
The discoverers assert that the cyanobacterium-like organisms metabolized sulfur (as there was little atmospheric oxygen then) and existed at a time when the Earth’s atmosphere was saturated with methane. The fossils have been dated to as early as 3.46 billion years and may indicate that oxygen-producing photoautotrophs (organisms that make their own food from sunlight, like the related blue-green algae), which are descendants of these organisms, may have evolved much earlier in the biotic history of the Earth.
If the biological nature of the fossils are confirmed, this would lend strong support to the view that life evolved relatively soon after the era known as the Late Heavy Bombardment (which ended about 3.85 billion ya) during which the early Earth was pummeled by asteroids, rendering the planet too hot (sterile) to evolve living creatures.
The paper — which makes no claim as to discovering the “oldest known fossils” — was published this past Sunday in the journal Nature Geoscience.
(Related topic) Earliest ancestor of modern placental mammals found in China.
Named Juramaia sinensis which means “Jurassic mother from China” the partial skeleton also contained impressions of soft tissue such as hair.
Previous DNA analysis of modern eutherians (ancestors of mammals with placentas, as opposed to metatherians, which are ancestors of marsupials) suggested that placental mammals should have appeared as early as 160 million years ago (when the differing mammalian groups began to diverge), but until this discovery, the earliest fossil find for this mammalian group was 125 mya.
The creatures forelimbs were adapted to tree-climbing — an ability that may have helped it escape larger predators of the period (unlike many of its ground-dwelling, mammal cousins). The ability also enabled the exploitation of a new ecological niche, which may account for the ultimate success of placental mammals.
The fossils were found in Liaoning Province in northeast China by a team of paleontologists led by by Carnegie Museum of Natural History paleontologist Zhe-Xi Luo.
Triassic period mass extinction of marine life blamed on methane gas “burp”
Two hundred million years ago, during the late Triassic period, half of the world’s marine animals were wiped out over a period of many thousands of years. Previous studies attributed this mass extinction to high CO2 levels from a prolonged period of intense vulcanism.
But new evidence uncovered by researchers from the Nordic Center for Earth Evolution (Univ. of Copenhagen, Denmark) now points to a different cause: a massive, methane “burp”.
The team, led by Micha Ruhl, measured carbon isotopes in plant fossils from before and after the extinction period and found that these carbon isotopes and other molecules were different from those found during the mass extinction event. Plus, the extinction period occurred over a much shorter time-scale (20 to 40, 000 years before the end-Triassic) than the volcanic period, which began 600, ooo years before the end of the Triassic period.
The team had to consider other sources of carbon that were capable of altering the Earth’s atmosphere on a massive scale. Methane gas (CH4) emerged as the most likely candidate. They estimated that the “burp” injected 12,000 gigatons of methane gas into the atmosphere. This huge amount of methane heated the air — and then the oceans — to such a degree that many marine species simply could not adapt to it, and perished.
The source of all this methane was probably trapped gas in frozen water (known as clathrates) in the sea floor which, when warmed, released the trapped gas. But, constant volcanic activity — injecting large quantities of heat-trapping CO2 over the previous thousands of years — was most likely the trigger of the massive methane release, theorize the researchers.
Second photo: (tubular microfossils) David Wacey
Third photo: (Earliest eutherian mammal) Mark A. Klinger, Carnegie Museum of Natural History
Fourth photo: (Northern Calcareous Alps, Austria) AAAS/Science via Discovery News