France has begun its first military exercises in space to test its ability to defend its satellites, in a sign of the growing competition between world powers in Earth's orbit.

Michel Friedling, the head of France's newly created Space Command, called the exercises a "stress test of our systems" and said they "were a first for the French army and even a first in Europe."

Codenamed "AsterX" in a nod to the first French satellite Asterix from 1965, the drills will simulate the monitoring of a potentially dangerous space object, as well as a threat to a satellite.

"A series of events appear and create crisis situations or threats against our space infrastructure, but not only this," Friedling told reporters from the Space Command headquarters in Toulouse in southwest France.

The new US Space Force and German space agencies are taking part in the French exercises, which began on Monday and will run until Friday.

France's Space Command was announced in 2019 and is set to number 500 people by 2025.

"Our allies and adversaries are militarising space... we need to act," Defence Minister Florence Parly said at the time.

University of Arizona researcher Jekan Thanga is taking scientific inspiration from an unlikely source: the biblical tale of Noah's Ark. Rather than two of every animal, however, his solar-powered ark on the moon would store cryogenically frozen seed, spore, sperm and egg samples from 6.7 million Earth species.

Thanga and a group of his undergraduate and graduate students outline the lunar ark concept, which they call a "modern global insurance policy," in a paper presented over the weekend during the IEEE Aerospace Conference.

"Earth is naturally a volatile environment," said Thanga, a professor of aerospace and mechanical engineering in the UArizona College of Engineering. "As humans, we had a close call about 75,000 years ago with the Toba supervolcanic eruption, which caused a 1,000-year cooling period and, according to some, aligns with an estimated drop in human diversity. Because human civilization has such a large footprint, if it were to collapse, that could have a negative cascading effect on the rest of the planet.

Astronauts face many challenges to their health, due to the exceptional conditions of spaceflight. Among these are a variety of infectious microbes that can attack their suppressed immune systems.

Now, in the first study of its kind, Cheryl Nickerson, lead author Jennifer Barrila and their colleagues describe the infection of human cells by the intestinal pathogen Salmonella Typhimurium during spaceflight. They show how the microgravity environment of spaceflight changes the molecular profile of human intestinal cells and how these expression patterns are further changed in response to infection. In another first, the researchers were also able to detect molecular changes in the bacterial pathogen while inside the infected host cells.

Russia and China agreed Tuesday to build a lunar space station, as Moscow seeks to modernise its extraterrestrial might and catch up with the United States in the space race.

Russia, which sent the first man into space during the Soviet Union, has been lagging behind Washington and Beijing in the exploration of the Moon and Mars.

Russia's space agency Roscosmos said in a statement that a memorandum was signed by its head Dmitry Rogozin and Zhang Kejian of China's National Space Administration (CNSA).

It said the lunar station will be designed as a "complex of experimental research facilities created on the surface and/or in the orbit of the Moon".

It would be available for use by other interested countries and international partners, the statement said, without details about the completion date.

Despite its former Soviet glory, Russia's space sector has suffered greatly in recent years from a lack of financing and corruption.

Moscow and Washington are collaborating in the space sector—one of the few areas of cooperation left between the Cold War rivals.

Russia last year lost its monopoly for manned flights to the International Space Station (ISS) after the first succesful mission of the US company Space X.