An atmosphere of exploration

Astronauts often look down on Earth and take pictures, creating a deep archive of images that are both beautiful and useful for science. But just as many NASA scientists and engineers have their eyes once again on the Moon, so too have astronauts.

A crew member aboard the International Space Station (ISS) took this photo in May 2022 as it orbits more than 400 kilometers (250 miles) above the Earth’s surface. At the time, the ISS was located above the South Pacific Ocean about 500 kilometers (300 miles) southwest of Tahiti.

Only a small part of the ocean is visible in this photo. Instead, the side view shows the Earth’s limb and layer upon layer of atmosphere. Clouds hover in the troposphere, the layer closest to the planet’s surface. Higher in the stratosphere and mesosphere, the sky darkens because there are fewer particles around to scatter light. In the distance, the waning gibbous Moon shines like a beacon through the thinnest layers of Earth’s atmosphere.

This rocky companion to Earth is at the center of NASA’s Artemis missions, which will return astronauts to the Moon while testing tools and ideas for human missions to Mars. One of the main goals of the uncrewed Artemis I mission is to ensure that the crew module can safely perform its entry and descent into the Earth’s atmosphere, as well as its landing and recovery. The next mission, Artemis II, will include a human crew.

This pair of photos shows NASA’s Space Launch System (SLS) rocket, with the Orion spacecraft on board, during preparations for the launch of Artemis I. NASA photographer Keegan Barber took the first photo on August 29 2022. The launch attempt that day was canceled when the rocket’s core stage engines failed to reach the proper temperature range. NASA photographer Bill Ingalls took the second photo at sunrise as launch preparations continued on August 31, 2022. The next launch attempt was scheduled for September 3.

In both photos, the launch site is framed by distinct features of our atmosphere. For example, the looming clouds testify to Florida’s great heat and humid air in the summer, when storms are almost daily. (As of August 31, sporadic rain showers were expected around the afternoon launch window of September 3.) In the sunrise photo, the low horizon appears red as more blue light is dispersed when sunlight has to get to our eyes through more gas particles in the atmosphere.

In contrast, the Moon has no atmosphere, at least not in Earth’s sense. Instead, the Moon has a very thin, tenuous layer of unbreathable gases known as the exosphere.

For the past five decades, astronauts have lived and worked in orbit around Earth, taking millions of photos of their home planet. In due time, they will once again observe their home across 240,000 miles of space.

Photograph of astronaut ISS067-E-70919 was acquired on May 21, 2022 with a Nikon D5 digital camera using a 420 millimeter lens and is provided by the ISS Crew Earth Observations Facility and Earth Science and Remote Sensing Unit, Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed on the NASA/JSC Gateway to Earth Astronaut Photography. Photographs by NASA/Keegan Barber and NASA/Bill Ingalls. Story by Kathryn Hansen.

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