Health & Science

A setback for hope of life on Mars

After sampling Martian air for more than a year, NASA’s Curiosity rover has detected almost no methane, dimming the prospects of finding life on the planet. Previous measurements—made by telescopes and orbiting spacecraft—suggested that Mars might harbor large quantities of the gas, which could be a sign of microbial life. Curiosity’s failure to detect methane on the planet’s surface is “a little disheartening,” mission scientist Sushil K. Atreya tells the Los Angeles Times. “If there were a lot of methane, it would imply a lot of things. It opens up the possibility of life.” Methane’s absence, however, doesn’t necessarily rule out life: Many types of bacteria don’t produce methane, and it’s possible that bacteria exist elsewhere on the planet, far from Curiosity’s base. It’s even plausible that methane disappears more quickly from the thin Martian atmosphere than from Earth’s, making it much harder for Curiosity to detect it, says mission scientist Paul Mahaffy. Curiosity has found evidence that Martian soil contains significant amounts of water, and that the planet was once covered in lakes and streams that could have supported life in the past. “It’s disappointing in that we didn’t get a pony for Christmas,” Mars Society President Robert Zubrin says of the lack of methane. “But it doesn’t mean there aren’t ponies out there.”

Secrets of the tiger genome

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Somewhere inside your cat, there’s a tiger. Researchers sequencing the genome of the Siberian tiger have discovered that it shares 96 percent of its genes with the common house cat. “Tigers are just a big domestic cat,” study author Jong Bhak of the Genome Research Foundation in South Korea tells BBCNews.com. He and his colleagues also sequenced the genomes of the African lion, the snow leopard, the white Bengal tiger, and the rare African white lion—all of which appear to have split from the house cat lineage around 11 million years ago. The big cats share 1,376 unique genetic attributes, many of which improved the cats’ ability to digest meat, while others appear to have conferred increased muscle strength and improved senses of smell and sight. Snow leopards have two mutations that help them live at high altitudes with little oxygen.

The nighttime cure for fear

The best time to dispel fearful memories may be during sleep, a new study by Northwestern University researchers has found. The researchers conditioned 15 volunteers to fear two specific faces by giving them uncomfortable electric shocks while they looked at images of them; they also paired each face with a distinctive odor, like lemon or mint. Then, when the volunteers were in the deepest phase of sleep, the researchers exposed them to one of the signature scents without shocking them. After the volunteers woke up, researchers showed them the faces again and measured their fear levels. The volunteers were no longer very afraid of the face matched to the scent they’d smelled in their sleep—presumably because they’d learned not to associate it with a shock. The fear reduction was achieved even though the subjects had no memory of anything happening while they were asleep. “We used to think you need awareness and conscious understanding of your emotional responses in order to change them,” Mount Sinai School of Medicine neuroscientist Daniela Schiller tells Nature.com. The research raises hopes that pre-existing phobias—and even post-traumatic stress disorders—might one day be effectively treated while patients sleep.

Hawaii’s molasses mess

A massive molasses spill in Honolulu Harbor is wreaking havoc on local marine life. Some 233,000 gallons of the brown goo leaked into the harbor from a broken pipeline belonging to the shipping firm Matson, and cleanup crews say the spill has already killed 26,000 fish. “It came as a shock to all of us,” Robert Harris, director of the Sierra Club of Hawaii, tells Phys.org. “I don’t think any of us were aware molasses even existed in Hawaii.” The viscous sugar product is heavier than oil and may be harder to remove: Instead of coating the surface of the water—where skimming could remove it—the molasses sank to the bottom, blanketing coral reefs and oxygen-producing sea grass. That led to the suffocation of fish and other marine creatures. Officials fear sharks will come in droves to eat the dead fish and are warning people to stay out of the water. Experts believe bacteria will eventually consume the molasses, but they don’t know what impact those bacteria will have on the environment. “We’ve never had a molasses spill,” says Hawaii Pacific University oceanographer David B. Field. “So I guess you could consider this an enormous experiment—of the most unfortunate kind.”