"The space station has been separate from Earth for 20 years," Rubins said.
We want to see what these closed environments do when they've been separate for a long time."
Sequencing DNA can reveal huge amounts of information, Rubins said, so applying sequencing to the station's microbiome can reveal a microbial picture of the space station -- and how it differs from Earth.
Since her previous stay on the station, there are new high-resolution microscopes on board she can use to study cells.
"This time around, it's all of the things on my bucket list," Rubins said.
Space milestone
The 20th anniversary of a continuous human presence on the space station occurs on November 1 during the beginning of Rubins' second six-month mission.
"It's so exciting -- we're at this wonderful time in space station history of operations for 20 years," she said.
"I know a lot of kids are struggling at home, so hopefully we can bring a little joy to talk about space exploration."
Full house
During their stay, these astronauts will also be joined by the SpaceX Crew-1 flight, bringing the total astronauts on the station to seven.
"It's going to be incredible to have seven people on the space station," Rubins said.