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Some of the startlingly bright terrain on Ceres' heavily cratered surface.

NASA's Dawn mission has achieved a number of firsts, including being the first spacecraft to go into orbit around two different bodies. The second of those destinations is Ceres, a dwarf planet that is by far the largest body in the asteroid belt. That visit has now shown us that a lot of our expectations for what we would find at Ceres were wrong: it's not an icy body, but liquid water has helped shape the dwarf planet's most dramatic features.

A couple of papers that analyze Dawn data have appeared in Nature journals this week. In one case, they suggest that the dwarf planet's composition is much rockier than we expected. But the other suggests that the mysterious bright spots found in some of Ceres' craters are the result of salty brines making their way to the surface.

Our thoughts about Ceres prior to Dawn's visit were dominated by the dwarf planet's relatively low density. This suggested to many people that it must be composed largely of water, although the surface was darker than you would expect from water ice that was expected to be a thin veneer over an icy world. Craters were also expected to be relatively scarce, as water ice is semi-viscous at the temperatures (120K and up) expected to be found on Ceres.

(credit: Thomas Hawk @ Flickr)

Airbags in cars have been responsible for saving many a life, but recent news might be tarnishing that reputation. More than 100 million cars worldwide are subject to the most complex automotive recall ever thanks to defective airbags from supplier Takata.

The problem rests with whether or not the airbag uses a chemical drying agent to prevent the ammonium-nitrate propellant charge from taking on moisture. Takata airbags without the drying agent may not work properly in an accident, filling the cabin with shards of metal shrapnel as well as the airbag. The National Highway Traffic Safety Administration (which ordered the recall here in the US) says that 10 people have been killed and more than 100 injured as a result.

If you drive one of the affected models, you may have to wait some time before getting it replaced. Takata has until 2019 to replace all the defective airbags and may well need the time; in the process of trying to have one of our cars fixed in June under the recall notice, we were told the supply chain was empty and that 2017 was more likely. But Takata isn't the only company having problems with prematurely exploding airbags.

(credit: Aurich Lawson)

The Wi-Fi Alliance industry group is now certifying products that can deliver multi-gigabit speeds and improve coverage in dense networks by delivering data to multiple devices simultaneously.

The new certification program, announced today, focuses on the so-called "Wave 2" features of the 802.11ac specification. 802.11ac is a few years old, but it includes several important features that were not available at launch. One such feature is MU-MIMO (multi-user, multiple-input, and multiple-output), which we wrote a feature on in May 2014. MU-MIMO is powered by multi-user beamforming technology that lets wireless access points send data streams to at least three users simultaneously. Without MU-MIMO, routers stream to just one device at a time but switch between them very fast so that users don't notice a slowdown except when lots of devices are on the network.

With the 80MHz channels supported in 802.11ac Wave 1, each data stream could provide up to 433Mbps and, when coupled with MU-MIMO routers, can send up to 433Mbps to at least three users simultaneously for a total of 1.3Gbps. But in addition to supporting MU-MIMO, Wave 2 also doubles the maximum channel bandwidth from 80MHz to 160MHz, boosting the potential throughput of each stream to 866Mbps. Wave 2 also supports four spatial streams instead of three, further boosting the theoretical maximum capacity. Technically, 802.11ac supports up to eight streams, but the certification program is still at four. Delivering eight streams with these data rates would use a lot of electricity.