Best Science Photos of the Week

Meet Riki-san and Haui-san, a cute and clumsy pair of clouded leopard cubs that made their debut this week at the San Diego Zoo.
The 14-week-old brothers came to Southern California by way of the Nashville Zoo at Grassmere, which has a breeding program aimed at boosting the numbers of this species, listed as vulnerable by the International Union for Conservation of Nature (IUCN).
[Full Story:
Baby Leopard Brothers Come to San Diego Zoo
]
New evidence hints that Venus may be volcanically active, which has long been a controversial topic among scientists.
Six years of observations by the European Space Agency's Venus Express spacecraft have shown significant changes in the sulfur dioxide content of the planet's atmosphere over time, which could be explained by a bout of volcanism.
[Full Story: Are Venus' Volcanoes Active? Clues Suggest Yes]
A European spacecraft orbiting Mars has snapped wintry-looking pictures of a mountain range on the Red Planet's southern highlands, where ridges and crater floors are dusted with carbon dioxide frost.
The pictures were captured by the high-resolution stereo camera on the European Space Agency's (ESA) Mars Express. They show part of Charitum Montes, a large group of rugged mountains stretching over nearly 620 miles (1,000 kilometers) near the southernmost rim of the Argyre impact basin. The brighter features represent a seasonal layer of carbon dioxide frost.
[Full Story: Mars Mountains Look Frosty in New Images
]
Xiao Liwu, the 4-month-old giant panda cub at the San Diego Zoo, is getting more svelte — though not less sleepy. The baby bear dozed off during his exam this week, caretakers said, but they were able to get a good look at him before his nap.
Tracy Clippinger, a veterinarian at the San Diego Zoo, said the cub's muscles are getting stronger and he is thinning out, improving his ability to crawl. Clippinger added that she counted eight teeth in his mouth and could feel more ready to break through the gums, before he fell asleep.
[Full Story:
Sleepy Panda Cub Gets Stronger
]
A new catalog aims to list all the known planets in the galaxy that could potentially be habitable to life. The count is at seven so far, with many more to come, researchers said.
The online listing, called the Habitable Exoplanets Catalog, celebrated its first anniversary today (Dec. 5). When it was first released last year, it had two potential habitable planets to its name. According to lead researcher Abel Mendez, the team expected to add maybe one or two more in the catalog's first year. The addition of five suspected new planets was wholly beyond anyone's expectations.
[Full Story: Exoplanet Catalog Reveals 7 Possibly Habitable Worlds]
Arctic glaciers retreated at record levels in 2012, while summer snow melted in the region much more rapidly than it has in the past, according to a new report by the National Oceanic and Atmospheric Association (NOAA).
The findings, presented here Wednesday (Dec. 5) at the annual meeting of the American Geophysical Union, are part of the annual "Arctic Report Card," which was assembled by more than 140 scientists to assess the state of the North Pole.
[Full Story:
Arctic's Record Melt Worries Scientists]
The moon and other rocky bodies in the inner solar system were pounded by long-ago impacts far more violently than previously thought, two NASA spacecraft have found.
NASA's twin Grail probes have created an ultra-precise gravity map of the moon, revealing that its crust is almost completely pulverized. The surprising find suggests that Earth, Mercury, Venus and Mars endured a similar beating billions of years ago, researchers said.
[Full Story: Moon Surprisingly Battered, New Lunar Gravity Map Reveals]
You may have seen Earth's lights from space — but never quite like this.
Today (Dec. 5), NASA and the National Oceanographic and Atmospheric Administration (NOAA) released a slew of images showing what the planet looks like when the sun goes down. The amazing images were announced in a news conference at the American Geophysical Union's annual meeting in San Francisco and were taken by an instrument aboard the Suomi NPP satellite in recent months.
[Full Story: Black Marble: Stunning New Images of Earth at Night]
Nature generally doesn't time its storms so well. A "Pineapple Express" weather system — so named because of its origins near the pineapple-rich Hawaiian Islands — dumped large amounts of rain on San Francisco and Northern California this past weekend, just ahead of the announcement of a new system for forecasting and assessing exactly that type of storm.
These storms, aptly and more technically known as atmospheric rivers, bring huge amounts of moisture across the Pacific. They are narrow bands in the atmosphere that funnel moisture from the tropics into more northerly latitudes. Over the course of several days, or even longer, the moisture in the system is dropped on a wide area and can potentially cause flooding and reservoir overflow, as has happened in some West Coast communities with the current system. That system also brought strong, hurricane-force winds to some regions and dozens of inches of snow to others.
[Full Story: 'Pineapple Express': New Sensors to Monitor Torrential Storms]
The young Earth may not have been a churning ball of scalding hot water, but a planet slightly cooler than today with more temperate oceans, according to two new studies.
The studies, presented Monday (Dec. 3) here at the annual meeting of the American Geophysical Union, may shed light on the paradox of the faint young sun: Why, despite the sun being 70 percent as bright as it is now, the early Earth during the Archean Eon (about 2.5 billion to 4 billion years ago) wasn't a giant snowball. Rather, it had a vast liquid water ocean filled with primitive microbes, ancestors to modern-day methane-producing and sulfur-eating microbes.
[Full Story: Fossilized Raindrops May Help Resolve Early Earth Paradox]
