We have lift-off. Freeze-dried mouse sperm that spent nine months in space has successfully impregnated female mice and created healthy offspring. We are starting to consider space colonisation more seriously, but there are still big questions about the viability of human reproduction off Earth. The high levels of cosmic radiation and low gravity could hinder conception or lead to abnormal development of a fetus, scientists say.
Science & Technology
Planting trees is often touted as a strategy to make cities greener, cleaner and healthier. But during heat waves, city trees actually boost air pollution levels. When temperatures rise, as much as 60 percent of ground-level ozone is created with the help of chemicals emitted by urban shrubbery, researchers report May 17 in Environmental Science & Technology.