Who needs a diary when you’ve got whale earwax? Hormone peaks, ocean pollutants, stress levels – it’s all there.

The plugs, which can weigh 250 grams and be 25 centimetres long, reflect annual migration patterns. During a blue whale’s six-month feeding season, earwax is light-coloured, filled with fat from its rich diet. As it fasts during migration, a darker layer forms. These layers allow scientists to age whales when they’re found dead.

Now, for the first time researchers have used the earwax to study a whale’s exposure to ocean contaminants from birth to death. “This has opened the floodgates for doing some great analysis,” says Sascha Usenko of Baylor University, Waco, Texas. “Now we can look at the impact of ocean contaminants on these organisms historically, which has always been very hard to address.”

Usenko and Stephen Trumble, also at Baylor University, shaved away at a plug from a 12-year-old male blue whale that was killed in a 2007 boating accident off the coast of California. The layers contained varying concentrations of DDT and flame-retardants. Exposure was highest during its first year, probably while the whale was nursing.

The plug also contained traces of hormones, which are broken down by the body and don’t leave records elsewhere. Testosterone levels peaked at 10 years, marking the beginning of sexual maturity, which can be difficult to determine but is important for conservation efforts. And levels of the stress hormone cortisol increased over the whale’s life, possibly because finding food, migrating and mating all got harder.

Usenko says the earwax method means we can look at how exposure to chemicals in the environment alters a whale’s stress levels, and how exposure today is different from exposure say, 50 years ago.

Journal reference:

Ancient rivers, their remains now lying beneath the Sahara desert, once formed green corridors at the surface which our ancestors followed on their great trek out of Africa.

A climate model has given us an image of what the landscape would have looked like around 100,000 years ago, suggesting that early humans went west out of sub-Saharan Africa and followed a vast and fertile river system to the Mediterranean.

For decades, there has been speculation that three now-dry North African rivers once served as green pathways for our early ancestors. The waterways would have supported lush flora and fauna to supply early humans with food as they trekked across the continent to the Mediterranean and on to Eurasia.

“But no one has been able to work out how much water was in these rivers, when and where exactly they flowed, and how far they reached across the desert,” says hydrologist Tom Coulthard of the University of Hull, UK.

Coulthard and his colleagues modelled the climate of the last interglacial period to see how the monsoon rains would have run down the trans-Saharan mountains’ north face and flowed across the landscape. Even after accounting for ground absorption and evaporation, the model indicated that there was enough water to have carved green corridors through the desert.

The most promising of the three reconstructed rivers, says Coulthard’s colleague Michael Rogerson, is the Irharhar, which flowed 800 kilometres due north to humid regions along the Algeria-Tunisia border.

Route to the coast

Intriguingly, it is the westernmost of the three systems, yet we know that humans eventually walked east out of Africa. Rogerson suggests that after reaching the end of the Irharhar, early humans may have taken advantage of marine resources and walked eastward along the North African coast, traversing the Nile delta before migrating into the Middle East.

“As they walked down the river, early humans would have had resources they could use immediately at the Irharhar’s far end,” he says. Any humans who followed the other two rivers would have been left stranded in inhospitable surroundings. “The other two rivers deliver you to the central parts of Libya, which we think were quite arid then.”

Archaeological evidence is more concentrated to the west, says Rogerson, tallying with the idea that most humans would have followed the Irharhar. Classic stone tools like spearheads have been found in the surrounding area, raising the possibility that early humans settled along the river’s banks.

Elena Garcea, an archaeologist at the University of Cassino, in Italy, who was not part of the study, told 91av she thought the model offered a new and clever way of distinguishing between existing theories of how our ancestors spread across the African continent and eventually migrated beyond.

Journal reference:

Meteorites baked in Earth’s hydrothermal vents might have released molecules crucial to forming cell-like membranes in early life forms. So suggest tests run on pieces of a van-sized meteor that broke up over California.

The meteor made headlines in April 2012 when it was spotted as a bright fireball over the US west. By tracking its trajectory, scientists were able to figure out where fragments should have landed and quickly collect relatively fresh pieces.

Initial tests on the pieces showed that the meteorite is a carbonaceous chondrite, a class that is usually rich in amino acids and other soluble, carbon-containing compounds. Scientists have theorised that these organics – key ingredients for life – dissolved from meteorites into Earth’s seas.

But it turns out that Sutter’s Mill was heated by collisions with other space rocks before it fell to Earth, which changed its composition. Other work found that the meteorite fragments seem to be oddly low in organic materials.

Hardly any soluble organics were found after boiling two more of the fragments, says of Arizona State University in Tempe. But her team also wanted to know how the insoluble material – the hardier and often ignored stuff in the meteorite – would withstand a six-day bake in extreme heat and pressures akin to those around hydrothermal vents, possible sites for the origin of life.

“And lo and behold, this meteorite left behind something we have never seen,” says Pizzarello. The unexpected riches were polyether- and ester-containing compounds. These long molecular chains, which contain carbon and oxygen, are insoluble but float in water, much like soaps or oils. They can form scaffold-like structures and may have trapped other, soluble organics within the cell-like enclosures of early life forms, she says.

Biochemistry bubbles

The long molecular chains probably formed during the extraterrestrial heating process and so would be unique to meteorites that endured lots of collisions, like Sutter’s Mill, says Pizzarello. Insoluble material from samples of other meteorites did not produce polyethers and esters when subjected to the same experimental heating. But the new result hints that some meteorites may have somehow wound up in hydrothermal vents and acted as time-release capsules, slowly letting go of vital insoluble compounds on early Earth.

“We can only speculate, but you can never say never,” says Pizzarello. “A meteorite that didn’t seem to be much may still have had the capability to form life. It’s important to think about what could have happened to the meteorite in the process of it being on Earth.”

Peter Jenniskens of the SETI Institute in Mountain View, California, led the search effort and several subsequent studies of the Sutter’s Mill meteorite.

“This paper describes some compounds that can create bubbles or small spaces that biochemistry can happen in, and that in itself makes the molecules interesting,” he says. “I’m excited to see that this meteorite produced some really unusual compounds. It makes the variety of compounds available for the origin of life more rich.”

Journal Reference: Proceedings of the National Academy of Sciences,

Video: Tourist spaceship takes longest, highest flight

The first vehicle purpose-built for carrying tourists into space has now tested not just its wings, but also its feathers.

Although it still hasn’t reached space, Virgin Galactic’s SpaceshipTwo flew slightly longer and higher than it did on its first powered flight in April – and this time it also deployed a safety mechanism called feathering as it descended back through Earth’s atmosphere.

The launch began at approximately 8 am local time yesterday, when the company’s WhiteKnightTwo carrier aircraft took off from Mojave, California. Once it reached an altitude of 14 kilometres, the carrier released SpaceShipTwo to fly by its own rocket power.

The spaceship then broke the sound barrier, accelerating to Mach 1.43 and reaching a maximum altitude of 21 kilometres. The engine burn lasted 20 seconds. That’s 4 seconds longer and about 4 kilometres higher than last time, on SpaceShipTwo’s first flight.

The craft’s rockets will have to sustain a 70 second flight to reach space, but Virgin Galactic founder Richard Branson was excited nonetheless. “This is a giant step,” he . “Our spaceship is now the highest commercial winged vehicle in history!”

For an onboard view of the flight, you can watch this video .

On its descent, pilots Mark Stucky and Clint Nichols manoeuvred the craft’s wings 65 degrees upwards into a shuttlecock-like position. Called feathering, that creates a powerful drag, allowing a slower, safer re-entry into Earth’s atmosphere.

Branson’s goal is to start commercial services in 2014, carrying an already long list of eager passengers on sub-orbital flights to space. Virgin Galactic signed up its 600th passenger for SpaceShipTwo in June.