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Solar System Exploration at 50
Exploration Stories: Favorite Historical Moments

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Active Worlds
Ralph Carruth
Manager, Materials and Processes Laboratory, Marshall Space Flight Center
Surveyor 1, the first of the Surveyor missions to make a successful soft landing on the moon, proved design and landing techniques. In addition to transmitting over 11,000 pictures, it sent information on the bearing strength of the lunar soil, the radar reflectivity and temperature.

What do you think are the most significant events that have occurred in the past fifty years of robotic planetary exploration? Why?

One of the first things to come to mind is the successful landing of the Surveyor 1 spacecraft on the moon. Surveyor 1 demonstrated our ability to be successful in such a complex endeavor as soft landing on another celestial body, and it also provided the first looks at the moon's surface. I was just a kid at the time, but I remember there were real concerns that the surface material might not even be able to support a vehicle landing there. This landing proved otherwise.

This image is the first photograph ever taken from the surface of Mars. It was taken by the Viking 1 lander shortly after it touched down on Mars on 20 July 1976.

The successful landings of the two Viking spacecraft on Mars were pivotal to our exploration of the Red Planet. Such missions were complicated and risky, but we were able to achieve them and this gave us a lot of confidence for the missions that followed. The Viking landers provided us with visions of the surface of Mars that were almost surreal. And the initial scientific information only urged us to ask more questions.

The boulder-strewn field of red rocks reaches to the horizon nearly two miles from Viking 2 on Mars' Utopia Plain. The salmon color of the sky is caused by dust particles suspended in the atmosphere.

Viking 2 landed 3 September 1976 -- about 4,600 miles from its twin, Viking 1, which touched down on July 20.

The results obtained from the Voyager spacecraft about worlds around Jupiter, Saturn and the other outer planets were beyond what we could have ever imagined. I worked at JPL during this time and the latest images were on monitors all around the center, even in the cafeteria. It was such an exciting time. With the flybys lasting only a limited time people working on the mission slept on cots or ran home for a nap and then returned to work, you couldn't get them to slow down.

The images were startling, and the information about volcanoes on Io, the rings of Saturn, the many moons ... continue to amaze us and added significantly to our understanding of these worlds.

This is an image of Saturn's C-ring and B-ring with many ringlets.

These spacecraft and those that followed have provided amazing discoveries about how active these worlds really are.

Voyager image of Saturn moon Enceladus. Enceladus' tiger stripes are known to spew ice from the moon's icy interior into space.

In this Voyager 2 image we see a close up of Miranda, a moon of Uranus. Miranda sports one of the strangest and most varied landscapes among extraterrestrial bodies.

This is the bright southern hemisphere on Triton. Voyager 2 found that Triton has active geysers, making it one of the few geologically active moons in our solar system.

Most striking to me were the initial pictures of the volcanoes on Io that were taken by Voyager.

In this image of Jupiter's moon Io by Voyager we see several active volcanoes.

You have to place the Mars Exploration Rovers (MER), Spirit and Opportunity, the little rovers that could, in the list of the most significant robotic planetary explorations we've conducted over the last 50 years.

This full-circle scene combines 817 images taken by the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. It shows the terrain that surrounded the rover while it was stationary for four months of work during its most recent Martian winter.

Their successful landing used a very non-traditional approach. Also, the images taken, the ground covered and the scientific data sent back to Earth have inspired and amazed people all over the world, and have given us so much information about Mars.

NASA's Mars Exploration Rover Spirit captured this stunning view as the sun sank below the rim of Gusev crater on Mars.

In your field of work, what are some examples of the great achievements and discoveries in planetary science and robotic exploration throughout the past 50 years?

A technician prepares Deep Space 1 for launch.

One of the advantages of solar electric propulsion for spacecraft primary propulsion is its high efficiency in using propellant and its ability to gather energy from the sun as opposed to being limited by what is chemically available from combusting propellants. This provides the promise of greater delta-velocity capability and the ability to perform very long missions to multiple destinations. This was demonstrated and effectively utilized by the Deep Space 1 spacecraft and the ongoing Dawn spacecraft for multiple rendezvous with comets and asteroids.

NASA's Dawn spacecraft obtained this image with its framing camera on 17 July 2011. It was taken from a distance of about 9,500 miles (15,000 km) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 0.88 miles (1.4 km).

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