These farmers grow maize, onions and other vegetables in a city in Ghana. They use groundwater to irrigate their crops. Nana Kofi Acquah/IWMI hide caption
The Philae lander took this photo of its descent onto comet 67P Wednesday, when it was about 3 kilometers from the surface. The landing site is seen with a resolution of about 3 meters per pixel. ESA/Rosetta/Philae/ROLIS hide caption
Chinese President Xi Jinping and President Obama, seen here during a ceremony at the Great Hall of the People in Beijing, announced pledges to reduce greenhouse gases. HUANG JINGWEN/Xinhua /Landov hide caption
Surprise! Not one of these things contains a single speck of blue pigment. Evan Leeson/Bob Peterson/lowjumpingfrog/Look Into My Eyes/Flickr hide caption
Britain's Andy Murray plays a return to Canada's Milos Raonic during their singles ATP World Tour tennis finals match Tuesday at the O2 arena in London. Tim Ireland/AP hide caption
Fishermen Ed Stewart (left) and Tannis Goodsen mend groundfishing nets on Merrill Wharf, in Portland, Maine, last November. Robert F. Bukaty/AP hide caption
David Quammen's new book is an extended excerpt of his previous one, Spillover, which explored how dangerous pathogens jump from animals to people. Courtesy of David Quammen hide caption
Europe's Rosetta spacecraft is about to send a lander to comet 67P/Churyumov-Gerasimenko. ESA/Rosetta/NavCam hide caption
This is a re-creation of a color plate from Interaction of Color, by Josef Albers. The two X's are are exactly the same — it's the different backgrounds that make them look like very different colors. Source: Josef Albers Interaction of Color hide caption
A section of a bike path that uses solar cells to produce electricity is opening for full-time use Wednesday. SolaRoad hide caption
Le Laboratoire Cambridge features a restaurant, the Cafe ArtScience. The restaurant's bar features a glass-globed drink vaporizer called Le Whaf. Andrea Shea/WBUR hide caption
A recent study found obese women are more likely than other women to work physically demanding jobs, like the kind that call for hard hats. They're less likely to work in jobs that require a lot of interaction with clients and customers — jobs that, on average, make more money. iStockphoto hide caption
Many artisan cheese producers never pasteurize their milk – it's raw. The milk's natural microbial community is still in there. This microbial festival gives cheese variety and intrigues scientists. iStockphoto hide caption
The "Aroma R-evolution" kit comes with four forks and 21 vials full of aromas like olive oil, mint and smoke. You drop a dab of scented liquid onto the base of the fork, and the smell is supposed to subtly flavor the food you eat while using the utensil. Claire Eggers/NPR hide caption
Middle Eastern Respiratory Syndrome virus particles cling to the surface of an infected cell. NIAID/Flickr hide caption