Though crying is a natural mechanism for emotional regulation, its manifestation in space raises intriguing questions. Astronauts, while floating in microgravity, still experience human emotions, and the way tears behave outside Earth's gravity offers a unique scientific perspective.
In 2013, Canadian astronaut Chris Hadfield, commander of the International Space Station (ISS), was asked on X (formerly Twitter) whether he could cry in orbit. He replied, “Can you cry in space? Your eyes make tears but they stick as a liquid ball. In fact, they sting a bit. So—space tears don't shed.”
On Earth, gravity pulls tears down, allowing them to wash away. In microgravity, the absence of that force causes tears to coalesce on the eyelid and cheek, forming a ball of liquid that eventually floats away when it reaches a critical size. This phenomenon was vividly demonstrated by Hadfield in a 2013 video where he let a droplet of water pool on his face; the droplet grew until it spilled over his nose, spread across his cheek, and finally floated into the cabin air.
In 2023, a study published in Frontiers in Psychology identified dry eye disease as one of the most common ocular conditions among ISS crew, with over 30 % reporting irritation and a “foreign body sensation”—the feeling of something stuck in the eye. The sudden introduction of moisture from a tear can therefore sting, echoing Hadfield’s remark about the “sting” of space tears.
Tears consist of three layers: an outer oily layer that prevents rapid evaporation, a middle aqueous layer that lubricates the eye, and an inner mucous layer that adheres the film to the cornea. Despite this complexity, the bulk of a tear is water, and water behaves the same in microgravity as on Earth—without gravity, it simply floats.
In practice, while astronauts can indeed produce tears, the lack of gravity means they cannot shed them in the familiar dripping manner. The resulting globules may become a visual reminder of the unique challenges of human physiology in space.
For more information, visit the NASA website and explore related research on ocular health in microgravity.
