Origin of life on land and not in the sea?

In an Early Edition Open Access article in PNAS “Origin of first cells at terrestrial, anoxic geothermal fields” Mulkidjanian et al. explore geochemical evidence for the origin of life on our planet. They find that all cells contain much higher amounts of potassium, phosphate and transition metals than any modern environments such as lakes, rivers and oceans, or for that matter reconstructed ancient such environments. They speculate that these higher levels of various elements are an inherited reflection of the inorganic environment in which the primordial cells were once formed, and use the geochemical composition to investigate suitable “cradles for life”.

Their results point to an origin of life, not in the oceans as we are used to, but in anoxic geothermal/volcanic fields on land, where the right geochemical conditions could be found. They argue that such anoxic geothermal/volcanic field on land could stay more or less unaffected by variations in the primordial climate for millions of years, long enough not only to form these “protocells” but also to sustain evolution of the first life forms.

In contrast to deep sea hydrothermal vents, which have also been suggested as “cradles of early life on Earth”, geothermal fields on land where subjected to weak solar light from the young sun which would probably be of benefit to the process.

It is a very interesting theory.

So perhaps life as we know it began on land, moved into the sea, diversified, evolved and then moved back on land billions of years later…

But how, when and why did the evolution process move into the sea?

Frozen Antarctic lakes and deep sea trenches are the new frontiers

“To boldly go where no man has gone before…”

In Antarctica a Russian team of scientists and engineers finally broke through to the ancient Lake Vostok, a sub-ice lake believed to hold stagnant water that could be millions of years old. After more than twenty years of stop-start drilling through the 3.7 km thick ice sheet covering Lake Vostok, drilling once again came to a halt.The inhospitable environment of the Antarctic forced the Russian team to postpone sampling and analyses until December 2012 when summer once again make working conditions possible.

In the meantime, the rest of the world will have to hold its breath wondering if the drilling operations may have contaminated the lake, or if the lake will prove to be sterile as some have suggested.

There are apparently several similar projects planned in some of the 350 sub-glacial lakes discovered in Antarctica. You can read more about the Lake Vostok-project on BBC-news.

Meanwhile in a totally different environment other scientists are turning their gaze to the deepest parts of our oceans, the deep-sea trenches, once believed to be too dark and cold to be able to host any life forms. But these trenches, which can be as deep as 11 km, are now known to be home to many animals and some that really surprise the scientists, e.g. the supergiant “shrimp” found 7 km down in the Kermadec Trench off New Zealand.

Space, and the search for extraterrestrial life, used to be the final frontier, but it is now challenged by remote and virtually unexplored areas on our own planet. Perhaps it is a sign of the times that we are turning our gaze inwards instead of outwards?

An issue of plants…

In a new issue of Nature Geoscience: Earth shaped by plants several interesting papers on plant related topics have been gathered for all us botany/palaeobotany interested geeks to feast on 🙂

The issue includes:

A feature/focus article by Timothy M. Lenton et al. on how the expansion of terrestrial vegetation in the Late Ordovician ca 440 million years ago cooled the atmosphere and triggered the growth of ice sheets.

A review article by Gibling & Davies on how the development of terrestrial vegetation changed the fluvial style of rivers and shaped the landscapes over a 250 million year period, from the Cambrian to the carboniferous.

As well as a selection of papers from the archives, amongst which are two articles dealing with the Triassic/Jurassic boundary, namely the paper by Belcher et al. (2010) on charcoal and wildfires in the T/J boundary record of Greenland, and a News and views story by Bas van de Schootbrugge (2010) discussing that very subject.

"What would life be without plants?"

The less spectacular period boundary of the Mesozoic…

I guess most people interested in geology and the history of life on Earth have heard about the dramatic period boundaries of the Mesozoic.

The most well known is of course the upper boundary of the Mesozoic, the Cretaceous-Paleogene boundary which marks the demise of the dinosaurs ca 65 million years ago. This boundary is marked not only by a catastrophic extraterrestrial impact, but is also contemporaneous to massive volcanism (Deccan Traps in India) and subsequent climatic and environmental  changes of these events.

Almost equally famous and marked by an even bigger mass extinction is the lower boundary of the Mesozoic, the Permian-Triassic boundary ca 251 million years ago, associated with the end-Permian mass extinction event when ca 95% of all life died out. The end-Permian event is linked to massive volcanism in Siberia and the longterm climatic and environmental consequences where so severe that the major part of the Triassic is characterised by a harsh arid hothouse climate.

Some have probably also heard of the Triassic-Jurassic boundary, ca 201 million years ago, also associated with a major mass extinction event linked to the perhaps largest large igneous province known, the Central Atlantic Magmatic Province – massive volcanism during the initial opening of the Central Atlantic – with severe climatic and environmental consequences.

Am I repeating myself? 😉

But how many have heard of the Jurassic-Cretaceous boundary ca 145 million years ago?

This less well-known period boundary is also marked by major climatic changes. At least on the northern Hemisphere. Palynological, sedimentological and geochemical studies bear witness of climatic change from predominantly arid to semi arid conditions in the latest Jurassic to more amicable humid conditions in the earliest Cretaceous of NW Europe (see e.g. our paper Lindström and Erlström, 2011 for references).

So far, this less spectacular period boundary has not been linked to any major volcanic events or extra terrestrial impacts. And now Valentin Fischer and his colleagues have published a study in PLoS ONE (read paper here) about one specific ischtyosaur that survived the less famous Jurassic-Cretaceous (J/K) mass extinction and in fact their study suggests that the J/K event hardly affected ischtyosaurs at all 😀