Astronauts have not yet set foot on Mars, but they are a step closer after the first test flight of Orion, NASA's new long-haul human spacecraft.

Orion is being developed by NASA to carry astronauts into space, but it is not simply a replacement for the Space Shuttle. The Orion capsule resembles that of the Apollo missions to the Moon and is destined for similar, far-flung destinations.

NASA is developing the spacecraft to first carry astronauts to an asteroid. But this first test could be a step toward realizing a centuries-old dream for humankind - landing humans on the surface of Mars.

Orion took off from Space Launch Complex 37 at Cape Canaveral Air Force Station. The craft was strapped to the top of the largest launch vehicle America has to offer: a towering United Launch Alliance Delta IV Heavy rocket. The launch window opened on Thursday at 7:05 am, but the day's launch attempts were thwarted by gusty winds and the launch was scrubbed.

NASA tried this morning and Orion sailed into Earth orbit perfectly when the launch window opened again at 7:05 am.

The launch had to be early in the morning in order to make sure the spacecraft would splash down into the ocean on its return to Earth when the Sun was still up, making it easier to identify the capsule bobbing in the waters of the Pacific Ocean.

Orion's crew module arrived in the Pacific Ocean off the coast of Baja at 11:29 a.m. Eastern Time. The capsule was collected by the recovery team from NASA, the U.S. Navy and Lockheed Martin, and towed to the deck of the USS Anchorage. It will be taken to San Diego and then transported by land back the NASA's Kennedy Space Center.

Tests, more tests, and a big splash
There were no astronauts on board Orion this time around, and the mission only lasted for two Earth orbits (roughly four and a half hours). However, the data that Orion returns will help NASA determine how much more work needs to be done in order to achieve the ultimate goal of reaching Mars.

The Delta IV Heavy is a big rocket, but in order to get to an asteroid and beyond, Orion will need something even more powerful. When all the tests are complete, the Orion spacecraft will be paired with the Space Launch System (SLS) rocket, which is also currently in development.

This flight, however, was all about testing technology and equipment on the Orion spacecraft itself in order to make sure everything is safe when astronauts eventually hop on board.

The first goal was to see how the stresses of launch affect Orion's critical systems, particularly during its re-entry into Earth's atmosphere.

To reach Earth's surface, Orion plowed down toward the planet at 20,000 miles per hour with a heat shield for protection. During this re-entry, it experienced about 80 percent of the heat it would have felt if it had traveled back to Earth from the Moon.

This was possibly the most dangerous part of the journey. As expected, Orion became surrounded by super-heated plasma during the descent and Mission Control lost contact with the craft for two and a half minutes. After the worst was over, the capsule began to slow as it dragged through the atmosphere and contact was re-established.

The descent was then slowed with parachutes, and finally the buoyant capsule splashed down in the Pacific Ocean off the coast of Baja California.

This re-entry process is a time-tested method from the early part of the Space Age, but the construction of Orion needed to be solid to pull it off.

The second major goal of this Orion flight was to collect data on the environment it encountered. The information will help scientists understand how Orion could fare on future and further missions into deep space.

Onboard Orion are lockers that carried commemorative objects into orbit, such as artwork, and a microchip full of names submitted by the public. Commemorating missions in this way is a long-standing tradition of spaceflight. Most of the lockers, however, were dedicated to science.

One contained a radiation experiment designed by students. The experiment was the winning entry in the Exploration Design Challenge, a contest that pushed students to develop methods for protecting astronauts from harmful radiation.

Another locker contained NASA's battery-operated independent radiation detector (BIRD). This experiment evaluates the radiation environment inside the locker as Orion traveled to the Van Allen belts. These 'belts' are zones of high radiation that sit high above the Earth's surface. When passing through them, a spacecraft and the passengers it carries experience a larger-than-normal radiation dose.

To reach the Van Allen Belts, Orion traveled farther into space than any human-rated spacecraft since Apollo (over four decades ago). Orion reached a peak distance of around 3,600 miles, about 15 times higher than the International Space Station.

With its radiation data, Orion is providing further information about one segment of a future Mars mission - launch to 3,600 miles. This adds to data collected by the Mars Science Laboratory (MSL) and MAVEN orbiter missions on their respective journeys to Mars. MSL's Curiosity rover is also currently collecting similar radiation data at the surface of Mars. In collecting all this data, scientists will be able to piece together a better model of the radiation environment that future missions will face from the Earth's surface to the surface of Mars.

Deep Space Science
In terms of astrobiology, putting astronauts on Mars could enable a wealth of new science investigations that only human beings can perform. A scientist exploring the surface can make in-the-moment decisions that robotic explorers are not yet capable of. But there are also benefits to the new technology in the short term before humans ever arrive at Mars.

All this new launch technology could enable larger, more capable science missions to travel farther and faster throughout the Solar System. Currently, the largest rover to touch down on Mars was carried away from Earth on an Atlas V rocket. This two-stage rocket is classed as a medium-heavy launch vehicle and has a thrust of 1,270 kilonewtons. The Orion test flight launched on a Delta IV heavy, which has a total thrust of 6,280 kilonewtons.

The next step for Orion is scheduled to be atop the new SLS, which will be capable of carrying even more mass than the Delta IV heavy. The technology that goes into developing a craft like the SLS could greatly expand our ability to launch science missions, from orbiters to surface explorers, to asteroids, the red planet and beyond.

A Future for Science
Scientists will now take all the data gathered from the Orion test flight and use it to improve the spacecraft's design. The hope is that an improved Orion will launch next atop a completed Space Launch System rocket. The added power of the SLS will propel Orion around the Moon for what has been dubbed "Exploration Mission-1."

When NASA completes construction of a second SLS rocket, it could be the launcher that returns astronauts to deep space. If progress on Orion continues as planned, the current generation of astronauts in training might be among the first humans to make it to Mars.

NASA has created a spectacular online tutorial about the goals of Orion and the technology being developed to achieve them. The NASA Orion Tutorial is available here