(left to right): NICOLE SPAULDING/CCI FROM C. P. LOVELUCK ET AL., ANTIQUITY 10.15184, 4, 2018; DANIEL RAMIREZ/FLICKR; NASA SCIENTIFIC VISUALIZATION STUDIO

Top stories: Earth’s darkest year, errors in ocean study, and a young crater under Greenland’s ice

Why 536 was ‘the worst year to be alive’

After analyzing volcanic glass particles in ice from a Swiss glacier, a team of researchers has identified why some medieval historians say 536 was the worst year to be alive. Early that year, a cataclysmic volcano in Iceland spewed ash across the Northern Hemisphere, creating a fog that plunged Europe, the Middle East, and parts of Asia into darkness—day and night—for 18 months. Summer temperatures dropped 1.5°C to 2.5°C, initiating the coldest decade in the past 2300 years.

High-profile ocean warming paper to get a correction

Scientists behind a major study on ocean warming this month are acknowledging errors in their calculations and say conclusions are not as certain as first reported. The research, published in Nature, said oceans are warming much faster than previously estimated. After a blog post flagged some discrepancies in the study, the authors said they would submit a correction to the journal.

Massive crater under Greenland’s ice points to climate-altering impact in the time of humans

An international team of scientists this week reported the discovery of a 31-kilometer-wide impact crater hidden beneath the Greenland Ice Sheet, left after a 1.5-kilometer-wide asteroid slammed into Earth. One of the planet’s 25 largest-known craters, it is also remarkably fresh, seemingly indicating a recent strike within the last few million years. The timing is still up for debate, but some researchers on the discovery team believe the asteroid struck at a crucial moment: roughly 13,000 years ago, just as the world was thawing from the last ice age.

Do gut bacteria make a second home in our brains?

At the annual meeting of the Society for Neuroscience in San Diego, California, last week, neuroanatomist Rosalinda Roberts made a splash with a presentation of results from her lab at the University of Alabama in Birmingham, in which bacteria was spotted inhabiting the cells of healthy human brains harvested from cadavers. Roberts was careful to note her team hasn’t ruled out the possibility of sample contamination, but the results are one of several preliminary indications that bacteria could directly influence processes in the brain.

Large, strangely dim galaxy found lurking on far side of Milky Way

Astronomers have discovered a dwarf galaxy, called Antlia 2, that is one-third the size of the Milky Way itself lurking on the far side of our galaxy. As big as the Large Magellanic Cloud, the galaxy’s largest companion, Antlia 2 eluded detection until now because it is 10,000 times fainter. Such a strange beast challenges models of galaxy formation and dark matter, the unseen stuff that helps pull galaxies together.