Roughly 70% water, Earth’s surface is covered with rivers, lakes, oceans, mud, and rain clouds. Scientists searching for alien life are searching for planets similar to our own, because experience tells us that life needs water in order to survive.

NASA’s Cassini spacecraft began photographing Titan, one of Saturn’s moons, in 2004. The pictures beamed back to Earth depict strange lakes and rivers. The European Space Agency (ESA)’s Huygens probe splashed into Titan’s mud in 2005, further convincing researchers that Titan was indeed “wet.”

The scientific community agrees that Titan appears Earth-like, but at temperatures around –290°F (–180°C), any water would be in the form of ice. Instead, astronomers believe any wetness on the surface of Titan is a combination of liquid methane, ethane, and other hard-to-freeze elements.

Apparently this moon doesn’t resemble Earth at all. Alex Hayes, a planetary scientist at Cornell University who works on the Cassini radar team, noticed something eerie while observing Saturn’s moon. “Where are all the waves?”

Wind, raindrops, and tides move Earth’s water in every direction. But Cassini has detected no wave action on Titan. It’s pretty strange, especially because, “[w]e know there is wind on Titan, the moon’s magnificent sand dunes prove it,” says Hayes.

Taking into account Titan’s gravity (one seventh that of Earth’s), the nature of fluids on its surface, and its dense atmosphere, Hayes and his colleagues calculated and published the speed needed for waves to form: only two miles per hour!

A strange puzzle, with even stranger solutions. Maybe the lakes are covered with tar, damping wave motion. Or they might be frozen. Or perhaps the wind hasn’t reached two miles per hour… yet.

Most of the lakes are located on Titan’s northern hemisphere, where it has been winter for a few years. The air during winter is colder and thicker, and may be the secret behind the missing waves.

If current climate models are correct, Cassini should be able to detect waves as Titan nears its summer solstice in 2017. Measurements and calculations of waves formed during the summer could tell us the chemical composition of Titan’s lakes… And reveal more about this Earth-like world so unlike Earth.

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA/JPL-Caltech/USGS

Last week, a letter published in Nature describes how scientists used newly available NASA satellite observations of rainfall and vegetation along with a model that predicts atmospheric wind flow patterns to explore the impact of Earth’s tropical forests. Their data show that the more vegetation the air had traveled over, the more moisture it carries and more rain is produced.  Air passing over extensive tropical forests produces at least twice as much rain as air passing over little vegetation. In some cases these forests increased rainfall thousands of kilometers away.

“We were surprised to find that this effect occurs strongly across more than half of the tropics,” says lead author Dominick Spracklen. “We found that the Amazon and Congo forests maintain rainfall over the periphery of the forest basins—regions where large numbers of people live and rely on rainfall for their livelihoods. Our study implies that deforestation of the Amazon and Congo forests could have catastrophic consequences for the people living thousands of kilometers away in surrounding countries.”

In fact, their research estimates that destruction of tropical forests would reduce rain across the Amazon basin by up to 21% in the dry season by 2050.

Spracklen continues, “This has significant implications for how policy makers should consider the environmental impacts of deforestation, since its effects on rainfall patterns may be felt not only locally, but on a continental scale.”

Another study, published two weeks ago in Science, shows chemically how the rainforest “seeds its own rain.”  A group of researchers, including our neighbors at the Advanced Light Source at Lawrence Berkeley National Laboratory (look for a Science in Action video about the ALS soon), examined aerosols from the air above a lush section of the Amazon rainforest.

Since water vapor needs something to condense upon, airborne particles become the seeds of liquid droplets in fog, mist and clouds. With examination, the researchers found that tiny grains of potassium salts are the basis of raindrops in the Amazon.

The salts are not generated by soot or the nearby Atlantic Ocean, but by the living things in the rainforest. Fungal spores seem to be one of the biggest contributors. In other words, the forest itself is causing the rain.

Image: Phil P Harris/Wikipedia

Oops!

Last winter we attended the AAAS Meeting in Vancouver, BC and listened to the University of Texas’ Charles Groat downplay the effects of fracking. We posted a bit of that news in an article about increased fracking regulations in April.

This week, Science Insider reports that Groat neglected to mention that he serves on the board of (and receives quite a bit of funding from) an oil and gas company that conducts fracking. Sounds like a bit of a conflict of interest, doesn’t it?

Really Old Polar Bears

In April we also ran a story about polar bear evolution. Researchers, studying nuclear DNA, put polar bears’ origin to 600,000 years ago.

But a new study, published earlier this week in the Proceedings of the National Academy of Sciences, suggests that polar bears evolved into a distinct species as many as 4-5 million years ago and did not recently descend from brown bears, despite shared genetic material.

The authors conclude that brown bears and polar bears interbred intermittently over the years. The New York Times compares this to humans in a funny, relatable way:

The progress of species formation, at least in this case, is a bit like a long, ambivalent divorce in which the two parties separate but occasionally fall back into bed even after the official decree.

Drought

Last week, we wrote about the devastating drought engulfing our country. This week Brandon Keim, writing in Wired, describes how this tragedy could reach beyond our borders and create global unrest.

Reporting on a recent study by the New England Complex Systems Institute, Keim says that commodity speculation (that food prices will rise due to the drought) may drive conflict in developing countries. The study reports that recent history demonstrates this trend:

During the last six years, high and fluctuating food prices have lead to widespread hunger and social unrest.

An article in Nature also explores this global impact.

Rain, rain…

Finally, earlier this summer, before drought was a harsh reality, we described mosquitoes amazing ability to fly through the rain. Now, a new study in Proceedings of the Royal Society B, demonstrates that hummingbirds are equally as adept in heavy downpours.

According to the abstract, UC Berkeley’s Victor Manuel Ortega-Jimenez and Robert Dudley found that:

…birds hovering in heavy rain adopted more horizontal body and tail positions, and also increased wingbeat frequency substantially, while reducing stroke amplitude when compared with control conditions.

These dynamics can be applied to robots, say the authors. No surprise, given both scientists are part of Berkeley’s Integrative Biology department—where many bio-inspired robotic ideas come from.

Image: User:Mdf/Wikipedia