SpaceX launched its 25th cargo mission to the International Space Station. Here's what's on board.

SpaceX's Dragon spacecraft lifted off the launchpad on July 14.
SpaceX's Dragon spacecraft lifted off the launchpad on July 14. (Image credit: NASA)

SpaceX launched its 25th cargo mission to the International Space Station (ISS) Thursday (July 14), carrying more than 5,800 pounds (2,630 kilograms) of supplies, along with equipment for NASA climate change research.

The supply mission, named CRS-25, blasted off from NASA's Kennedy Space Center in Florida aboard a SpaceX Falcon 9 rocket. After just 2.5 minutes of flight, the first stage of the rocket detached, making a safe, upright landing five minutes later on SpaceX's drone ship "A Shortfall of Gravitas" in the Atlantic Ocean. The second stage of the rocket continued upward into orbit, propelling itself and the uncrewed Dragon resupply craft mounted on its nose. 

The Dragon craft is expected to slowly catch up with the ISS and reach it Saturday morning (July 16) at around 11:20 a.m. EDT. After Dragon docks with the orbiting lab, astronauts will unload the capsule's payload, which includes fresh food and supplies, as well as scientific equipment for the ISS's dozens of active scientific investigations. 

One of the mission's bulkiest and most important deliveries is the equipment for the Earth Surface Mineral Dust Source Investigation (EMIT). Once affixed to the outside of the ISS, this experiment will scan Earth to study how dust from arid regions travels on winds and affects the climate. (Scientists still don't know if mineral dust has an overall warming or cooling effect.)

Related: Here's every spaceship that's ever carried an astronaut into orbit

"Understanding the dust composition is key to understanding the warming versus cooling and by how much, both on regional and global scales," Roger Clark, a senior scientist at the Planetary Science Institute in Tucson, Arizona, and a co-investigator on the EMIT mission, said in a statement. "Depending on the composition of the dust, it can cool or warm the planet. Dark dust, including dust with iron oxides, may cause warming, whereas light dust may result in cooling. Dust also plays a role in ecosystems and human health."

Despite the importance of dust in climate models, it has remained understudied. 

"Currently, the dust impacts of climate change are based on about 5,000 samples of soil for the entire Earth," Clark said. "EMIT will collect more than 1 billion usable measurements for the arid regions of the world." 

EMIT can precisely measure the contents of Earth's dust from space by using a technique called imaging spectrometry, in which inbound light is separated into distinct wavelengths ranging from the ultraviolet to the infrared. Because particular minerals inside dust clouds reflect only certain wavelengths, EMIT can identify the composition of dust clouds by breaking them down into 288 possible colors. After this identification, the spectrometer will use unique software to map the detected materials to their locations around the globe.

CRS-25's launch has been a long time coming. Originally scheduled to lift off more than a month ago, the mission was held back three times after engineers discovered potentially unsafe levels of corrosive hydrazine vapor — a fuel used in Dragon's Draco thrusters — in the craft's propulsion system. NASA and SpaceX technicians inspected the rocket extensively before finally giving it the green light.

Other experiments on their way to the ISS will examine the effects of aging on cellular repair and investigate whether those effects can be reversed in astronauts after they return to Earth, as well as study the viability of making concrete from materials found on the low-gravity environments of the moon and Mars.

Originally published on Live Science.

Ben Turner
Staff Writer

Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.