Microgravity in space perturbs human physiology and is detrimental for astronaut health, a fact first realized during early Apollo missions when astronauts experienced inner ear disturbances, heart arrhythmia, low blood pressure, dehydration, and loss of calcium from their bones after their missions.

One of the most striking observations from Apollo missions was that just over half of astronauts became sick with colds or other infections within a week of returning to Earth. Some astronauts have even experienced re-activation of dormant viruses, such as the chickenpox virus. These findings stimulated studies on the effects of weak gravity, or "microgravity," on the immune system, which scientists have been exploring for decades of manned rockets launches, shuttle travel and space station stints, or sometimes by simulating space gravity in earthbound labs.

In the last study led by one of the first women astronauts, Millie Hughes-Fulford, Ph.D., researchers at UCSF and Stanford University now have shown that the weakening of an astronaut's immune system during space travel is likely due in part to abnormal activation of immune cells called T regulator cells (Tregs).

Tregs normally are triggered to ramp down immune responses when infection no longer threatens and are important regulators of immune responses in diseases ranging from cancer to COVID-19.

It's been 30 years since Nasa last visited Venus, with the Magellan orbiter in 1990. Now, two new missions have been selected to explore the deadly atmosphere, crushing pressures and volcanic landscape.

The process dates back to February 2020, when Nasa announced that four missions were to undergo a nine-month peer-review process for feasibility. They were all part of the Discovery program, started by Nasa in 1992 to bring together scientists and engineers to create exciting, groundbreaking missions. Set aside from the flagship missions—such as Curiosity and Perseverance—the missions operating under Discovery have taken unique and innovative approaches to exploring the solar system.

The two winning Venus missions, Davinci and Veritas, have been awarded US$500 million (£354 million) and will be launched some time between 2028 and 2030. But the competition was tough from the two losing missions, which would have gone to Io and Triton, respectively moons of Jupiter and Neptune.