Astronauts aboard the International Space Station have successfully grown a flower to a full bloom for the first time outside our Earth.

Scott Kelly of the U.S. space agency NASA tweeted this weekend that a zinnia has flowered in the microgravity environment of the orbiting laboratory, along with an accompanying photo of an orange flower with 13 petals.

"First ever flower grown in space makes its debut! #SpaceFlower #zinnia #YearInSpace," wrote Kelly, adding: "Yes, there are other life forms in space!"

A NASA article explained that zinnias were chosen not for their beauty but to "help scientists understand how plants flower and grow in microgravity."

Previously, other plants such as wheat and romaine lettuce have been grown in space. When a batch of lettuce was harvested in August on the space station, NASA astronauts were even allowed to eat the fruits of their labor for the first time.

Growing zinnias seemed to post more challenges to in-orbit gardeners than growing a vegetative crop such as lettuce.

"The zinnia plant is very different from lettuce," said Trent Smith, NASA's Veggie project manager. "It is more sensitive to environmental parameters and light characteristics. It has a longer growth duration between 60 and 80 days. Thus, it is a more difficult plant to grow."

Just more than two weeks into their growth period, astronauts noted that water was seeping out of some of the crop's leaves, a condition that occurs when a plant is experiencing high humidity.

To fix it, they adjusted the speed of the station's veggie facility fan from low to high to dry them out, but that didn't prevent two of the plants from dying. The remaining two plants continued to thrive and one of them eventually blossomed into a flower this weekend.

More crops will be sent to the space station this year, including Chinese cabbage and romaine lettuce. NASA said the lessons learned from these plants will help grow tomatoes in 2018.

The implications of plant life for space missions are very significant, including helping boosting astronauts' spirits while they're working there.

"Plants can indeed enhance long duration missions in isolated, confined and extreme environments - environments that are artificial and deprived of nature," said Alexandra Whitmire, deputy scientist for the Behavioral Health and Performance element in the NASA Human Research Program.

"While not all crew members may enjoy taking care of plants, for many, having this option is beneficial."

In the long term, plant experiments will yield important information in preparation for a Mars mission.

"In future missions, the importance of plants will likely increase given the crews' limited connection to Earth," Whitmire said. "Studies from other isolated and confined environments, such as Antarctic stations, demonstrate the importance of plants in confinement, and how much more salient fresh food becomes psychologically, when there is little stimuli around."