This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Giant viruses - perhaps more ordinary than not?
A new study published in Science by Shulz et al. indicates that at least one group of giant viruses may have simply accumulated its enormous genome (larger in some instances than certain bacteria) by cobbling genes together over time. This represents a counter-argument to the idea that giant viruses - replete with genetic code for proteins that include translation system components - are some form of 'de-evolved' cellular organisms. In this case, rather than representing tantalizing evidence for a 'fourth domain' of life on Earth, the phylogenomic analysis of the giant Klosneuviruses points towards a relatively recent accumulation of genetic material from the cellular host species. In short, these 'baggy' sheathed viruses just happen to be at a genetically replete point in their evolution.
Ground ice and landslides on Ceres
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Data from NASA's Dawn spacecraft have revealed that the asteroid/dwarf-planet/minor planet (oh come on folks, let's just call these things planets!) Ceres has a number of 'flows' or landslides across its surface that suggest a mixture of water ice and rocky rubble - not unlike places on Earth. In Nature Geoscience, Schmidt et al. point out that Dawn has only found direct evidence for water ice on Ceres in a small number of locations. But their analysis of a variety of flowing/sliding features is consistent with a much wider distribution of water, mixed in with the other components of Ceres's outer layers. Bottom line: 10-50% by volume of these layers is likely to be ice, and by extension this could mean that the outer asteroid belt indeed represents a significant reservoir of ancient water.
The hunt for Planet Nine
The search continues for direct and indirect evidence of a proposed large planet (number nine, or ten, or whatever you want) somewhere out in the distant solar system - perhaps 700 times further from the Sun than the Earth. This world could explain severe peculiarities in the configuration of the known orbits of a number of smaller trans-Neptunian objects. In a paper by de León et al. published in the Monthly Notices of the Royal Astronomical Society, spectroscopic evidence is presented suggesting that two of these extreme trans-Neptunian objects with near-identical orbits (bodies of a few hundred kilometers in size with the dull names of 2004 VN112 and 2013 RF98) are also very similar in composition. The authors propose that these bodies could have once been a binary system - bound by their mutual gravitational pulls.
Based on extensive orbital simulations it seems possible that about 5 to 10 million years ago this pair was broken up by the influence of a much larger body. What was that larger object? It could have been Planet Nine.