The NASA DART probe's view of Dimorphos shortly before impact.

NASA has forever changed the Didymos-Dimorphos system by attempting to divert an asteroid. The test shows that a planetary defense strategy could be used to protect Earth.

The 1,340-pound spaceship smashed into the moonlet on September 26 after 10 months in the asteroid system. Astronomers kept a close eye on the pair in hopes of detecting a change to the system's dynamics.

Data sets gathered by ground-based optical and radio telescopes show that the period around Didymos changed from 11 hours and 55 minutes to 11 hours and 23 minutes.

It is the first time in history that humanity has changed the trajectory of a planetary object.

Bill Nelson opened the press briefing by saying that NASA was serious about defending the planet. The $308 million DART test was described by the NASA administrator as a "watershed moment for humanity" and he's right about it.

The analysis was made possible by four different optical observatories in South Africa. The two independent data sets both pointed to the same answer of 32 minutes.

Hubble Space Telescope image showing the aftermath of the DART collision, including a comet-like tail emanating from the moonlet.

The minimal amount of time needed for a successful demonstration is what would have made the DART team happy. She explained that the adjustment was within the bounds of the models but at the extreme upper end.

The large amount of material kicked up from the surface by the collision may have enhanced the impact. The DART was travelling at over twenty thousand miles per hour when it hit the asteroid. Astronomers were unsure if Dimorphos was a solid body or a loose conglomeration of rocks going into the mission.

Tom Statler, DART program scientist at NASA, said he didn't think Dimorphos would last 73 seconds. The recoil from the asteroid's surface material was a major factor in the change. It was like being in a balloon.

Dimorphos is now tens of meters closer to Didymos and more tightly bound to its larger host after the test. The system itself is 11 million km from Earth and the asteroids are 0.75 miles away.

DART may have done more than shorten Dimorphos's flight around Didymos. There is a chance that the impact introduced a wobble. Future observations are required to confirm this. Statler said that there is a lot of work that needs to be done to understand what happened.

The impact had a large effect on the system in the hours and days after it happened. The Italian LICIACube, which came along for the journey, took photos after the impact. The amount of debris kicked up by the impact was revealed by the views from ground-based telescopes. The tail of dimorphos is caused by solar winds blowing the fine-grained particles away from the moonlet.

DART is a huge success, but there are still a lot of things to be done. Not all asteroids have loose collections of debris, so scientists will want to measure the effects of similar impacts on more solid targets. The most important priority right now is to complete our inventory of asteroids that are potentially dangerous to Earth.

NASA's upcoming Near- Earth Object Surveyor should help immensely in this regard.

NASA's DART is no longer and this future probe is hoping to take a second look.