Mitochondria—A billion years of cohabitation

Mitochondria—A billion years of cohabitation

An engulfment of a small bacterium by a larger archaeon more than a billion years ago resulted not in death, but in one of the most successful partnerships on earth. As you sit there, each of your cells (apart from your red blood cells) contains hundreds or thousands of the descendants of that bacterium, still earning their keep as part of that endosymbiotic deal struck in some ancient pool. Ho...

The First Four Billion Years

Ten Billion Years of Galaxy Evolution

Observations in the Hubble Deep Fields have been used to study the evolution of galaxy morphology over time. The majority of galaxies with z < 1 are seen to be disk like, whereas most objects with z > 2 appear to be either chaotic or centrally concentrated “blobs”. Such blobs might be the ancestral objects of ellipticals or of galaxy bulges. About 1/3 of objects with z > 2 appear to be in the p...

Life: the first two billion years.

Microfossils, stromatolites, preserved lipids and biologically informative isotopic ratios provide a substantial record of bacterial diversity and biogeochemical cycles in Proterozoic (2500-541 Ma) oceans that can be interpreted, at least broadly, in terms of present-day organisms and metabolic processes. Archean (more than 2500 Ma) sedimentary rocks add at least a billion years to the recorded...

Early formation of the Moon 4.51 billion years ago

Establishing the age of the Moon is critical to understanding solar system evolution and the formation of rocky planets, including Earth. However, despite its importance, the age of the Moon has never been accurately determined. We present uranium-lead dating of Apollo 14 zircon fragments that yield highly precise, concordant ages, demonstrating that they are robust against postcrystallization ...