12 | NewScientist | 22/29 December 2012

IT SEEMS size does matter in the brain. Even the smallest stroke can cause widespread damage.

Researchers led by David Kleinfeld of the University of California, San Diego, induced tiny strokes in rats by blocking blood vessels called arterioles, stopping blood from reaching capillaries deeper in the brain.

Blocking just a single arteriole caused cell death in all directions

for hundreds of micrometres after the blockage. Block several and you can knock out entire brain regions as the damage travels even in areas still fed by intact vessels. It was previously assumed that strokes on this scale would be innocuous.

The damage impaired the animals’ ability to judge when a gap between two platforms was too wide to cross. But giving the

Frigid Nile flows on Saturnian moon

COURSING 400 kilometres towards a dark delta, a river found on Saturn’s moon Titan is the longest yet seen outside Earth. Bearing a striking resemblance to the Nile, the river hints at active geological activity on the moon.

At -179 °C, Titan is too cold for flowing water. Instead, liquid hydrocarbons such as methane fill its lakes and streams. Spotted by the Cassini spacecraft, the newfound river follows a nearly straight path into one of Titan’s large seas, Ligeia Mare.

The Nile’s relatively straight shape is partly controlled by fault lines, which on Earth mark the places where tectonic plates meet. Titan is probably too small to have plates, but the river may also be tracing a fault, says Thomas Farr of NASA’s Jet Propulsion Laboratory in Pasadena, California. Pressure could build up on such faults, causing them to shift and form new chasms, he says.

Trojans were quick to adapt in a post-war world

EVEN ancient cities knew about rebranding. Troy was destroyed by war about 3200 years ago – an event that may have inspired Homer to write the Iliad, 400 years later. But the famous city rose again, reinventing itself to fit a new political landscape.

Troy lies in north-west Turkey and has been studied for decades. Pottery made before the war has a distinct Trojan style but after the war its style is typical of the Balkans. This led archaeologists to believe that the locals had been forced out and replaced by populations from overseas.

But when Peter Grave at the University of New

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Even tiny strokes wreak havoc in brain rats injections of memantine – a drug already approved to treat people with Alzheimer’s disease – within 45 minutes of the stroke prevented both the damage and loss of function even when multiple vessels were blocked (Nature Neuroscience, DOI: 10.1038/nn.3278).

In people, these “silent” mini-strokes go unnoticed and are undetectable by brain scans, says Kleinfeld, but could have an impact on brain function over time.

England in Armidale, Australia, and his colleagues examined the chemical make-up of the pottery, they realised that both pre and post-war objects contained clay from exactly the same local sources, suggesting the same people were making the pots.

“There is substantial evidence for cultural continuity,” says Grave. So if the Trojans never left the city, why did their pottery style change?

Before the sack of Troy, the city looked east towards the powerful Hittite Empire. But this political powerhouse collapsed around the time that Troy was destroyed. Grave says the post-war pottery is Balkan in style because the Trojans were keen to align themselves with the people there, who had become the new political elite in the region (Journal of Archaeological Sciences, doi.org/js8).

PEERING through a cosmic fog, the Hubble Space Telescope has seen the earliest known galaxies. This group of seven objects dates back to the reionisation era, when radiation was breaking down the light-blocking neutral hydrogen that filled the early universe.

Hubble identified one galaxy as the most distant object known, which existed 13.4 billion years ago (arxiv.org/abs/1211.6804). Such galaxies probably emitted the radiation that caused reionisation, says Richard Ellis of the California Institute of Technology in Pasadena.

Ellis adds that Hubble has probably seen as far as it can. Deeper views will have to wait for the James Webb Space Telescope, due to launch in 2018.

Hubble spots most faraway galaxy

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