The Curiosity rover has made its most unusual find to date on Mars: rocks made of pure sulfur. And it all began when the 1-ton rover happened to drive over a rock and crack it open, revealing yellowish-green crystals never spotted before on the red planet.

“I think it’s the strangest find of the whole mission and the most unexpected,” said Ashwin Vasavada, Curiosity project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “I have to say, there’s a lot of luck involved here. Not every rock has something interesting inside.”

The Curiosity team was eager for the rover to investigate the Gediz Vallis channel, a winding groove that appears to have been created 3 billion years ago by a mix of flowing water and debris. The channel is carved into part of the 3-mile-tall (5-kilometer-tall) Mount Sharp. The rover has been scaling the mountain since 2014.

White stones had been visible in the distance, and the mission scientists wanted a closer look. The rover drivers at JPL, who send instructions to Curiosity, did a 90-degree turn to put the robotic explorer in the right position for its cameras to capture a mosaic of the surrounding landscape.

The upper stage from a Chinese rocket that launched a batch of Internet satellites Tuesday has broken apart in space, creating a debris field of more than 300 objects in one of the most heavily-trafficked zones in low-Earth orbit.

US Space Command, which tracks objects in orbit with a network of radars and optical sensors, confirmed the rocket breakup Thursday. Space Command said the event created more than 300 pieces of trackable debris. The military's ground-based radars are capable of tracking objects larger than 10 centimeters (4 inches).

The culprit is the second stage of China's Long March 6A rocket, which lifted off Tuesday with the first batch of 18 satellites for a planned Chinese megaconstellation that could eventually number thousands of spacecraft. The Long March 6A's second stage apparently disintegrated after placing its payload of 18 satellites into a polar orbit at an altitude of roughly 500 miles (800 kilometers).

NASA is about to make its most important safety decision in nearly a generation

As soon as this week, NASA officials will make perhaps the agency's most consequential safety decision in human spaceflight in 21 years.

NASA astronauts Butch Wilmore and Suni Williams are nearly 10 weeks into a test flight that was originally set to last a little more than one week. The two retired US Navy test pilots were the first people to fly into orbit on Boeing's Starliner spacecraft when it launched on June 5. Now, NASA officials aren't sure Starliner is safe enough to bring the astronauts home.

Three of the managers at the center of the pending decision, Ken Bowersox and Steve Stich from NASA and Boeing's LeRoy Cain, either had key roles in the ill-fated final flight of Space Shuttle Columbia in 2003 or felt the consequences of the accident.

At that time, officials misjudged the risk. Seven astronauts died, and the Space Shuttle Columbia was destroyed as it reentered the atmosphere over Texas. Bowersox, Stich, and Cain weren't the people making the call on the health of Columbia's heat shield in 2003, but they had front-row seats to the consequences.