Here’s a round-up of recent science headlines we didn’t want you to miss!

Ancient Rivers

Without a smart phone or GPS device, how did early humans find their way out of Africa? A study published last week in PLoS One determines that ancient rivers, now covered by the Sahara Desert, provided habitable routes to follow.

Simulating paleoclimates in the region, the researchers found evidence of three major river systems that likely existed in North Africa 130,000–100,000 years ago, but are now largely buried by dune systems in the desert. When flowing, these rivers likely provided fertile habitats for animals and vegetation, creating “green corridors” across the region.

“It’s exciting to think that 100,000 years ago there were three huge rivers forcing their way across 1000-km of the Sahara desert to the Mediterranean—and that our ancestors could have walked alongside them,” says lead author Tom Coulthard of the University of Hull, UK.

Cosmic Beginnings?

Did life on Earth hail from Mars, as one researcher proposed last month, or comet collisions? Apparently, in both cases, it all has to do with the chemistry. Carl Zimmer, one of our favorite science writers, has a recent New York Times article about the chemistry needed to produce DNA from RNA. And while it doesn’t look like early Earth had those compounds, Mars might have.

Then, earlier this week, a study published in Nature Geoscience finds that the collision of icy comets with planetary bodies could result in the formation of complex amino acids, the building blocks of proteins (and life).

The researchers suggest that this process provides another piece to the puzzle of how life was kick-started on Earth, after a period of time between 4.5 and 3.8 billion years ago when the planet was being bombarded by comets and meteorites.

The team made their discovery by recreating the impact of a comet by firing projectiles through a large high-speed gun. This gun, located at the University of Kent, uses compressed gas to propel projectiles at speeds of 7.15 kilometers per second into targets of ice mixtures, which have a similar composition to comets. The resulting impact created amino acids such as glycine and D- and L-alanine. Sounds like a fun method of discovery…

Speaking of fun collisions, if you want more of them, the Morrison Planetarium at the Academy is featuring Cosmic Collisions in its current show rotation. From the our website:

Creative and destructive, dynamic and dazzling, collisions are a key mechanism in the evolution of the Universe.

Missing Mars Methane

One chemical Mars seems to be missing? Methane. The gas was sought as a possible sign of microbial life currently living on the seemingly barren world. However, despite earlier reports that NASA’s Mars rover, Curiosity, discovered methane on the red planet, NASA reports today in Science that none has been found.

Curiosity’s earlier evidence of methane detection turned out to be within leftover air from Earth. And previous reports of localized methane concentrations up to 45 parts per billion on Mars were based on observations from Earth and from orbit around Mars.

“It would have been exciting to find methane, but we have high confidence in our measurements,” says the report’s lead author, Chris Webster. “We measured repeatedly from Martian spring to late summer, but with no detection of methane.”

But don’t give up on microbial Martians just yet… “This important result will help direct our efforts to examine the possibility of life on Mars,” says NASA’s Michael Meyer. “It reduces the probability of current methane-producing Martian microbes, but this addresses only one type of microbial metabolism. As we know, there are many types of terrestrial microbes that don’t generate methane.”

Looking for extraterrestrial life? Next month’s Brilliant!Science festival can deliver it to you. Visit this page for more information.

Image: the Tunable Laser Spectrometer on-board Curiosity: NASA/JPL-Caltech

Carbon dioxide is often the bad guy—warming the world and acidifying the ocean. But it’s not the only bad guy; there are other pollutants humans release into the air that damage our planet. And halting the release of those chemicals might be the key in beginning to stop the Arctic melt and to limit sea level rise.

As glaciers and ice sheets melt and warming oceans expand, sea levels rise by about 3 millimeters annually (just more than one-tenth of an inch). If temperatures continue to increase, sea levels are projected to rise between 18 and 59 centimeters (7 to 23 inches) this century.

Carbon dioxide can last in the atmosphere for hundreds of years, so it will take centuries to feel the positive effects of any actions we take now to limit CO₂—too late to protect many coastal communities on the front lines of sea level rise. However, other greenhouse emissions such as methane, tropospheric ozone, hydrofluorocarbons, and black carbon last for a far shorter time, anywhere from a week to a decade.

Previous research has shown that a sharp reduction in emissions of these shorter-lived pollutants beginning in 2015 could offset warming temperatures by up to 50 percent by 2050. Researchers at Scripps Institution for Oceanography, the National Center for Atmospheric Research (NCAR) and Climate Central decided to study how the same reductions in these pollutants might affect the rate of sea level rise. The team found that such cuts could dramatically slow rising sea levels—to an estimated 22 to 42 percent by 2100.

The research is published in Nature Climate Change.

“It is still not too late, by stabilizing carbon dioxide concentrations in the atmosphere and reducing emissions of shorter-lived pollutants, to lower the rate of warming and reduce sea level rise,” says co-author Veerabhadran Ramanathan of Scripps. “The large role of the shorter-lived pollutants is encouraging since technologies are available to drastically cut their emissions.”

Methane emissions can come from waste, agricultural practices and burning natural gas. Tropospheric ozone is often called the bad ozone and results from the interaction of sunlight with chemicals emitted by burning fossil fuels. Hydrofluorocarbons are emitted from refrigeration and air conditioning. And black carbon is basically soot—caused by diesel fuels and burning biomass like wood, a basic fuel source in many developing nations.

“It must be remembered that carbon dioxide is still the most important factor in sea level rise over the long term,” says NCAR’s Warren Washington, another co-author. “But we can make a real difference in the next several decades by reducing other emissions.”

Image: NASA

Despite being in the wrong place, at the wrong time, we were able to catch incredible glimpses of the solar eclipse this week through photos throughout the web.

DNA sequencing started the year off right. Popular Science reported that “For the First Time, DNA Sequencing Technology Saves A Child’s Life.” Doctors, desperate to find the cause of a boy’s severe illness, sequenced his genes, discovered a mutation and were able to prescribe a treatment that appears to be working. A new machine could make this practice more common. An article in the New York Times this week described a more affordable sequencing machine. At $50,000, the Personal Genome Machine is significantly less than standard machines and “could expand the use of DNA sequencing from specialized centers to smaller university and industrial labs, and into hospitals and doctors’ offices.”

What is causing birds to fall out of the sky and fish to die from Arkansas to Maryland and Brazil to Sweden? Cold weather? Hail storms? Fireworks? The end of the world? There’s been much hype and speculation, but scientists don’t appear to be worried. The Academy’s own Jack Dumbacher is getting samples from the southern occurrences—he’s planning on testing the corpses for viruses. You can track these deaths yourself through Google maps or the US Geological Survey.

Finally, after topping the science news headlines last year, oil in the Gulf reappeared this week, at least on news sites. Have bacteria consumed nearly all of the methane from the spill? A study published in Science this week suggests that’s the case. Ed Yong finds a lot of support for the paper in his blog on Discover; Samantha Joye tells Science News, “Just because you can’t find methane in the spot where you lowered your [instruments] doesn’t mean there’s no methane out there somewhere.”

Also, the president’s oil spill commission released the first chapter of its report this week. (The entire report will be available next week.) An excerpt from the chapter in Science Insider reports that the blame for the disaster can be shared among the companies responsible for the well.

Most of the mistakes and oversights at Macondo can be traced back to a single overarching failure—a failure of management.

And sadly, this may not be an unusual event, according to the New York Times:

The commission warned that without major changes, another such accident was likely.

If you want a front seat on a Gulf of Mexico recovery expedition, follow Sylvia Earle and others on National Geographic News Watch this month.

What science news did you dive into this week? Share with us!

Image by Brydzo/Wikimedia