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Uranium isotopes in subglacial precipitates from the Wilkes Basin of the East Antarctic Ice Sheet reveal ice retreat during a warm Pleistocene interglacial period about 400,000 years ago.

A list of authors and their affiliations appears at the end of the paper New-particle formation is a major contributor to urban smog(1,2), but how it occurs in cities is often puzzling(3). If the growth rates of urban particles are similar to those found in cleaner environments (1-10 nanometres per hour), then existing understanding suggests that new urban particles should be rapidly scavenged by the high concentration of pre-existing particles. Here we show, through experiments performed under atmospheric conditions in the CLOUD chamber at CERN, that below about +5 degrees Celsius, nitric acid and ammonia vapours can condense onto freshly nucleated particles as small as a few nanometres in diameter. Moreover, when it is cold enough (below -15 degrees Celsius), nitric acid and ammonia can nucleate directly through an acid-base stabilization mechanism to form ammonium nitrate particles. Given that these vapours are often one thousand times more abundant than sulfuric acid, the resulting particle growth rates can be extremely high, reaching well above 100 nanometres per hour. However, these high growth rates require the gas-particle ammonium nitrate system to be out of equilibrium in order to sustain gas-phase supersaturations. In view of the strong temperature dependence that we measure for the gas-phase supersaturations, we expect such transient conditions to occur in inhomogeneous urban settings, especially in wintertime, driven by vertical mixing and by strong local sources such as traffic. Even though rapid growth from nitric acid and ammonia condensation may last for only a few minutes, it is nonetheless fast enough to shepherd freshly nucleated particles through the smallest size range where they are most vulnerable to scavenging loss, thus greatly increasing their survival probability. We also expect nitric acid and ammonia nucleation and rapid growth to be important in the relatively clean and cold upper free troposphere, where ammonia can be convected from the continental boundary layer and nitric acid is abundant from electrical storms(4,5).

Massive disk galaxies like the Milky Way are expected to form at late times in traditional models of galaxy formation(1,2), but recent numerical simulations suggest that such galaxies could form as early as a billion years after the Big Bang through the accretion of cold material and mergers(3,4). Observationally, it has been difficult to identify disk galaxies in emission at high redshift(5,6) in order to discern between competing models of galaxy formation. Here we report imaging, with a resolution of about 1.3 kiloparsecs, of the 158-micrometre emission line from singly ionized carbon, the far-infrared dust continuum and the near-ultraviolet continuum emission from a galaxy at a redshift of 4.2603, identified by detecting its absorption of quasar light. These observations show that the emission arises from gas inside a cold, dusty, rotating disk with a rotational velocity of about 272 kilometres per second. The detection of emission from carbon monoxide in the galaxy yields a molecular mass that is consistent with the estimate from the ionized carbon emission of about 72 billion solar masses. The existence of such a massive, rotationally supported, cold disk galaxy when the Universe was only 1.5 billion years old favours formation through either cold-mode accretion or mergers, although its large rotational velocity and large content of cold gas remain challenging to reproduce with most numerical simulations(7,8).

A massive rotating disk galaxy was formed a mere 1.5 billion years after the Big Bang, a surprisingly short time after the origin of the Universe.

Molecular analyses of newly discovered, embryo-bearing ornithischian and sauropod dinosaur eggs suggest that the ancestral dinosaur egg was soft-shelled, and that hard-shelled eggs evolved independently at least three times in the major dinosaur lineages.

Quantum mechanics governs the microscopic world, where low mass and momentum reveal a natural wave-particle duality. Magnifying quantum behaviour to macroscopic scales is a major strength of the technique of cooling and trapping atomic gases, in which low momentum is engineered through extremely low temperatures. Advances in this field have achieved such precise control over atomic systems that gravity, often negligible when considering individual atoms, has emerged as a substantial obstacle. In particular, although weaker trapping fields would allow access to lower temperatures(1,2), gravity empties atom traps that are too weak. Additionally, inertial sensors based on cold atoms could reach better sensitivities if the free-fall time of the atoms after release from the trap could be made longer(3). Planetary orbit, specifically the condition of perpetual free-fall, offers to lift cold-atom studies beyond such terrestrial limitations. Here we report production of rubidium Bose-Einstein condensates (BECs) in an Earth-orbiting research laboratory, the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with free-expansion times extending beyond one second, providing an initial demonstration of the advantages offered by a microgravity environment for cold-atom experiments and verifying the successful operation of this facility. With routine BEC production, continuing operations will support long-term investigations of trap topologies unique to microgravity(4,5), atom-laser sources(6), few-body physics(7,8)and pathfinding techniques for atom-wave interferometry(9-12).