The moon (Photo: NASA)

The Earth and its moon started with a big bang, according to a new theory from NASA scientists, who believe both were born out of collisions between two massive developing planets.The new theory suggests the two giant planetary bodies, each about five times the size of Mars, collided with each other twice.

After the first collision, the planets smashed into each other again, leaving behind material which resulted in our early Earth. The fledgling planet was surrounded by a disk of left-over material, which later combined to form the moon.

This new theory challenges the widely-held “giant impact hypothesis,” which suggests the moon formed early in our solar system’s history after an enormous impact between Earth and a Mars-sized planet that was still being formed.  Some call that protoplanet Theia, after the mother of the goddess of the moon in Greek mythology.

However, skeptics say if the Theia theory were true, Earth and the moon would have different chemical compositions from each other, which they don’t.

Iconic photo of the Earth and moon as seen from the Apollo 8 spacecraft while in lunar orbit on 12/24/1968. (Photo: NASA)

According to the new NASA theory, the two collisions, along with the subsequent melding of left-over material, formed both the Earth and the moon, which is why they have similar chemical compositions. “Our understanding of the solar system is constantly being refined with each new discovery,” says NASA’s Greg Schmidt. “This research illustrates the importance of modeling planetary formation to enhance our scientific understanding of the moon and its place in the solar system.”

The model which demonstrates this new theory was developed at the Southwest Research Institute (SwRI), in San Antonio, Texas by Robin M. Canup.

Canup says her work was inspired by previous studies on the early history of the moon, which explain the similar chemical composition of the Earth and moon, while at the same time producing an appropriate mass for Earth and the moon.

“The ultimate likelihood of each impact scenario will need to be assessed by improved models of terrestrial planet formation,” Canup said.  Canup’s work is outlined in Science.

Video: A computer simulation of a low-velocity collision of two protoplanets that contain 45 and 55 percent of the Earth’s mass. Colors indicate particle temperature in kelvin, with blue-to-red indicating temperatures from 2,000 K to in excess of 6,440 K. After the first protoplanetary impact, they re-collide, merge and form a rapidly spinning Earth-mass planet that is surrounded by a disk of particles that would later form the Moon. (Video: Southwest Research Institute)

Artist rendition of the InSight Lander at work on the surface of Mars. (Photo: JPL/NASA)

NASA just can’t get enough of Mars.  Two weeks after successfully landing  the much-ballyhooed rover Curiosity on the red planet, officials at the U.S. space agency announced that yet another  mission to Mars is set for 2016.

The InSight mission, which stands for “Interior Exploration using Seismic Investigations, Geodesy and Heat Transport,” will investigate deep below the Martian surface to see why the planet developed differently than Earth.

InSight, according to NASA, will be more than a mission to Mars. Officials hope  this terrestrial planet explorer will  answer some long-held questions about planetary and solar system science, including the processes that went into forming the rocky planets of the inner solar system -Mercury, Venus, Earth, and Mars- more than four billion years ago.

Unlike the Mars explorers currently cruising the planet’s surface, the InSight lander is designed to stay put while several sophisticated instruments do the heavy lifting.

While a robotic arm and two cameras help set and monitor all of the gear placed on the planet’s surface, an onboard geodetic instrument will determine the rotational axis of Mars.

Other devices include one that measures the seismic waves traveling though the interior of Mars, as well as a subsurface heat probe designed to gauge the heat flow from the planet’s interior.

The InSight mission is getting assistance from international partners including the French space agency, CNES, which is contributing the seismic monitoring equipment. The German Aerospace Center is slated to  provide the subsurface heat probe.

Mission team members for InSight, the new Mars lander mission selected by NASA to launch in 2016, explain how the spacecraft will advance our knowledge of Mars’ history and rocky planet evolution.

The InSight mission was selected from three finalist proposals which were chosen from many in May 2011. The two rejected missions included putting a spacecraft on the surface of a comet, while the other proposed a mission to Saturn’s moon Titan.

“The exploration of Mars is a top priority for NASA, and the selection of InSight ensures we will continue to unlock the mysteries of the Red Planet and lay the groundwork for a future human mission there,” NASA Administrator Charles Bolden said. “The recent successful landing of the Curiosity rover has galvanized public interest in space exploration and today’s announcement makes clear there are more exciting Mars missions to come.”

Scheduled for launch in March 2016, InSight is expected to land on Mars in September 2016 for a 720-day mission.