Washington: There NASA Expedition 42 crew members returned safely to the Earth on Thursday after a 167-day mission at the International Space Station (ISS) that included several scientific experiments and spacewalks to prepare the ISS for future arrivals by the US commercial space taxis.

Commander Barry Wilmore of NASA and flight engineers Alexander Samokutyaev and Elena Serova of the Russian Federal Space Agency (Roscosmos) touched down in their capsule southeast of the remote town of Dzhezkazgan in Kazakhstan, the space agency said in a statement.

During their time on station, the crew members participated in a variety of research focusing on the effects of microgravity on cells, the Earth observation, physical science and biological and molecular science.

One of several key research focus areas during Expedition 42 was human health management for long-duration space travel, as NASA and Roscosmos prepare for two crew members to spend one year aboard the space station.

The space station also serves as a test bed to demonstrate new technology.

The Cloud-Aerosol Transport System (CATS) arrived and was installed during Expedition 42, and already is providing data to improve scientists’ understanding of the structure and evolution of the Earth’s atmosphere.

This may lead to enhancements to spacecraft launches, landings and communications systems; help guide future atmospheric investigations of Mars, Jupiter or other worlds; and help researchers model and predict climate changes on the Earth.

The station crew also welcomed three cargo spacecraft with several tonnes of scientific investigations, food, fuel and other supplies.

In January, the trio helped grapple and connect a SpaceX Dragon spacecraft on the company’s fifth contracted commercial resupply mission to the station.

The Dragon returned to the Earth in February with critical science samples.

During his time on the orbital complex, Wilmore ventured outside the space station with NASA astronaut Terry Virts on three spacewalks to prepare for new international docking adapters and future US commercial crew spacecraft.

Expedition 43 currently is operating the station, with Virts in command.

Flight engineers Anton Shkaplerov of Roscosmos and Samantha Cristoforetti of ESA (European Space Agency), are continuing station research and operations until three new crewmates arrive in two weeks.