The final launch of the summer of Mars missions is nearly underway.

On Thursday, NASA hopes to send a robotic rover and a small experimental helicopter on a journey of six and a half months to the red planet. It follows two earlier launches by the United Arab Emirates and China.

NASA was originally scheduled to lift off earlier in July, but had to overcome a number of technical delays that pushed back the launch. While it is last to leave, all three missions should arrive at the red planet at about the same time, in February.

NASAs Perseverance rover will lift off from the Cape Canaveral Air Force Station in Florida on Thursday at 7:50 a.m. Eastern time.

The launch, aboard a United Launch Alliance Atlas V rocket, is being streamed live by NASA on its website. Or you can watch it in the video player below:

The rocket with the rover on top was rolled out to its launchpad on Wednesday, and about two hours before the scheduled launch time, U.L.A. reported that fueling had started.

Weather looked promising, with an 80 percent chance of favorable conditions for launch.

Perseverance is a car-size wheeled robot nearly identical in design to NASAs previous Mars rover, Curiosity, which landed in 2012. However, Perseverance is headed to a different place a crater named Jezero that was once a lake carrying a different set of instruments. Curiosity was designed to look for habitable environments, and it found signs of a freshwater lake. Perseverance is to go a step farther and search for evidence of past life that might have lived in the lake at Jezero.

Perseverance is also carrying a couple of devices that are more fun than scientific: several cameras, which will record various views as the spacecraft zooms through the atmosphere en route to landing; and two microphones, which will be the first to record sounds on another planet.

It is carrying an experimental helicopter, too.

Yup, its called Ingenuity. The four-pound Marscopter is a technology experiment, and if it works, it will be the first powered flight on another planet. The rotors have to spin at 2,4000 revolutions a minute to generate lift in the thin atmosphere of Mars, just one percent as dense at Earths at the surface.

A couple of experiments on Perseverance have nothing to do with searching for past life, but they could help future life on Mars astronauts from Earth.

One of the crucial supplies that astronauts will need is oxygen, for breathing and as a rocket propellant.

The Mars Oxygen In-Situ Resource Utilization Experiment, or MOXIE, will take carbon dioxide molecules from the Martian atmosphere and split them into oxygen atoms and carbon monoxide.

MOXIE will try to demonstrate that is possible on the surface of the red planet. But the amount of oxygen it could produce less than ounce per hour is tiny.

Were only making about enough oxygen to keep a small dog alive, said Michael Hecht, the principal investigator for MOXIE.

But if the idea works, the technique could be employed in the future on a much larger scale to fill up a rocket. So astronauts in a future Mars mission could take off from Mars to come home, he said.

Perseverance is also carrying samples of materials used in spacesuits, mounted on a target used to calibrate one of the rovers instruments.

When I send somebody to Mars in my spacesuit, I want to make sure that they stay alive that whole time, Amy Ross, one of NASAs spacesuit designers said during a news conference on Tuesday.

With Perseverance taking repeated measurements over a couple of years on Mars, we can understand how our materials hold up or dont in that environment, she said.

Perseverance will land on Mars on Feb. 18 next year at 3:40 p.m. Eastern time.

Every 26 months, Earth and Mars come close to each other, which allows the quickest, most efficient trip from Earth to Mars. If the launch does not occur by the middle of August, NASA would have to wait until the next opportunity, in 2022.

Jezero crater was filled with water about 3.5 billion years ago when Mars was warmer and wetter. From orbit, earlier NASA spacecraft spotted a dried-up river on one side of Jezero and an outflow channel can be seen on the other side. The sediments of a fan-shape delta can be seen where the river spilled into the crater. No one knows if anything ever lived on Mars, but if it did, Jezero would be a prime place to look, scientists decided.

Landing on Mars is difficult. The planets thin atmosphere isnt thick enough to provide enough drag to slow down a spacecraft like Perseverance, which will be arriving at more than 12,000 miles per hour. But the atmosphere is still thick enough to generate thousands of degrees of heat, complicating the task of slowing down Perseverance before it slams into the ground. Quite a few landing attempts by NASA and other space agencies have ended with creating new craters on the red planets surface.

But NASA has pulled off five consecutive successful landings. To increase the likelihood that Perseverance rover will be the sixth, NASA has made adjustments to the parachute that slows the spacecraft when it reaches the Martian atmosphere. It has also improved the rovers ability to identify a smooth landing site.

The Emirates Mars Mission successfully lifted off on a Japanese rocket on July 20.

The space program of the United Arab Emirates is modest, and its bid to join the ranks of countries that have reached Mars is part of an ambitious effort to inspire Emirati youth to take up careers in science and technology.

Its Hope spacecraft will orbit Mars for a number of years, helping scientists study the planets weather cycles.

China launched the second mission, Tianwen-1, on July 23.

The countrys space program has seen a number of successes in recent years, including two rovers that landed on Earths moon as well as a pair of space stations deployed in orbit. But its previous attempt to get to Mars in 2011 was lost when the Russian rocket it was riding on failed and burned up in Earths atmosphere.

The new Chinese mission includes an orbiter, a lander and a rover. While other countries have taken a staggered approach to visiting Mars an orbiter first, then a lander, then finally a rover China emphasizes that it will attempt to operate all of these components for the first time at once.

The orbiter, according to four scientists involved in the mission, will study Mars and its atmosphere for about one Martian year, or 687 days on Earth. In addition to two cameras, the spacecraft carries subsurface radar, a detector to study the Martian magnetic field and three other scientific instruments.

The rover will try to land in the Utopia Planitia region in the mid-northern Martian latitudes. NASAs Viking 2 mission touched down there in 1976. Earlier studies using data from NASAs Mars Reconnaissance Orbiter showed that Utopia Planitia has a layer of water ice equivalent to what is found in Lake Superior on Earth.

If it manages the perilous Martian landing, the rover will use a mix of cameras, ground-penetrating radar and other instruments to better understand the distribution of underground ice, which future human colonists on Mars could use to sustain themselves. Chinas mission is to last about 90 Martian days.

A fourth mission, the joint Russian-European Rosalind Franklin rover, was to launch this summer, too. But technical hurdles, aggravated by the coronavirus pandemic, could not be overcome in time. It is now scheduled to launch in 2022.

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NASAs Mars Perseverance Rover Launch: When to Watch - The New York Times