Scientists designed centimeter-wide featherweight disks that could float without a power source in Earth’s mesosphere, the thin air of Mars or other places with low levels of atmosphere. The tiny devices may even be able to carry a payload. The researchers simulated low atmosphere environments in a chamber and used lasers to mimic sunlight. They devised disks of various sizes and tested how well each stayed afloat.

How it works: The prototype disks are made from two thin, perforated membranes of aluminum oxide connected by minuscule vertical supports. They are kept aloft by a force called photophoresis: Gas molecules bounce more forcefully off the light-warmed side of an object than they do off the cooler one, creating airflow. In this case, the research team coated the bottom of each disk with chromium so it would absorb light and heat up more than the top. Gas molecules pinging off the lower part gained more momentum than those at the top, generating lift. Carefully calibrated holes in the disk’s structure increased this thrust, using an effect called thermal transpiration which passively channels the air from cooler to warmer regions.

Why this matters: Our mesosphere, which extends about 50 to 85 kilometers above the planet’s surface, is sometimes called the “ignorosphere”—it’s too high for aircraft and weather balloons to reach but too low for satellites to access, making it one of Earth’s least-studied regions. In the future, swarms of these surfing disks might collect atmospheric data and relay telecommunications not only in Earth’s mesosphere but also in the atmosphere of Mars.

Doctor visits for flulike illnesses in the U.S. have reached their highest level in nearly 30 years, according to the CDC. So far this season, influenza viruses have led to more than 120,000 hospitalizations and 5,000 deaths, including nine children. More than 8 percent of all visits to a health care provider in the week ending on December 27 were for respiratory illness—the highest rate since the CDC started keeping tabs on such visits in 1997.

Why this is happening: A new variant of the influenza A strain H3N2 that is known as subclade K may be driving up infections: the variant has been shown to carry mutations that may make this year’s flu vaccine less effective. But the shots still provide some protection, especially against severe disease and death, experts say.

The coming weeks: The new numbers don’t cover the post-holiday-travel period, so the rates of doctor visits and hospitalizations could rise even further.