Pioneer Plaque Replica Shows Humanity's First Spacecraft-Flown Message to Aliens

The first NASA probes to leave our solar system carried a message for extraterrestrial life designed by Carl Sagan that would showcase Earth and humanity.

In 1972 and 1973, humanity launched two probes that for the first time would leave our solar system. Sending a spacecraft so far from home inspired a small group of people to wonder, what if we included a message to aliens on it? If aliens found the spacecraft, small as the chance would be, it would be a chance to showcase Earth and humanity.

This led to NASA including one plaque each on the Pioneer 10 and Pioneer 11 spacecraft, launched by the space agency to study Jupiter and Saturn. After their primary missions were done, the spacecraft flew at escape velocity speed from the solar system. We lost contact with both spacecraft years ago due to power constraints and their vast distance from Earth, but they continue to sail silently in the cosmos.

A new Kickstarter campaign will let you take a replica of one of these plaques home. Conceived by designer Duane King – whose portfolio advertises work for companies such as Apple, Google, and Nike – the replica will be made of gold-anodized aluminum with the original design, and recreated from the original manufacturer.

"A billion years from now, when everything we've ever made has crumbled into dust, the Pioneer plaques will still be floating out there in space — a message in a bottle cast into a vast cosmic ocean," said King in a statement.

King said he first became interested in space when watching the 1980s series Cosmos hosted by science popularizer and Cornell University astronomer Carl Sagan. (This was a predecessor to the 2014 series hosted by Neil deGrasse Tyson.) Sagan played a central role in bringing the Pioneer plaque to life, and also assisted with the more famous Voyager record that flew on the Voyager 1 and 2 spacecraft in the 1970s. The Voyager record is being replicated after a hugely successful Kickstarter campaign earlier this year.

The most famous part of the Pioneer design is a golden plaque, featuring a design engraved into a gold-anodized aluminum plate, according to NASA. The plate was roughly 6 inches by 9 inches and attached to the antenna support struts of the spacecraft to lessen any erosion from dust encountered in space.

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"The suggestion of a message on Pioneer 10 was brought to Dr. Carl Sagan mere months before launch — a staggeringly brief period in the timescale of the design and test of spacecraft," wrote the Planetary Society, which was co-founded by Sagan before his death in 1996. "Sagan passed along the idea to NASA, and to his surprise, the suggestion was embraced and approved by every level of the hierarchy. At that, Sagan joined Professor Frank Drake of Cornell University and, Sagan’s then-wife, artist Linda Salzman Sagan, to craft this extraterrestrial message."

The plaque is based on measurements of the hydrogen atom. Hydrogen is the most prevalent element in the universe, and is often found in stars (such as our own sun.) At top left of the plaque are two hydrogen atoms in different states of energy. When hydrogen transitions to a higher energy state, it releases electromagnetic radiation at a wavelength of 21 centimeters.

The 21 centimeters was used as a unit of measurement to show human height, the Planetary Society said. At right, you can see figures of a man and a woman, who were posed in gestures to indicate welcome and that the human body is moveable and flexible. Beside the woman is the number 8 in binary code (which is commonly used in computers), with two ticks at the head and foot of the woman to represent her height. Her height is therefore 8 units high, or 8x21 centimeters = 168 centimeters (5.5 feet).

The large diagram at left shows the sun (at center) with a map to find it. Surrounding it are relative distances to pulsars, or very dense stars that rotate quickly and send out signals rapidly and regularly. At bottom you can see a map of our own solar system, with the sun (at left) and (from left to right) what were considered the nine planets in the 1960s: Mercury, Venus, Earth, Mars, Saturn, Jupiter, Uranus, Neptune and Pluto.

NASA maintained contact with the Pioneer 10 spacecraft until 2003, and Pioneer 11 until 1995. It is still in touch with the Voyager 1 and Voyager 2 spacecraft. In August 2012, Voyager 1 was the first spacecraft confirmed to cross the boundary to interstellar space, leaving the solar system behind forever.

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