Gliese 581d is the outlying planet in the Gliese 581 system, and orbits its parent star every 66.8 days. It may be covered by a large and deep ocean and is the first serious 'waterworld' candidate discovered beyond our Solar System.

Credit: ESO

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SYDNEY: What would you like to say to aliens? That's the question COSMOS is asking of the people of Earth over the next two weeks, as we give you the opportunity to send a text message to the nearest Earth-like planet.

“It’s like a ‘message in a bottle’ cast out into the stars," said Wilson da Silva, editor of COSMOS. "What’s interesting is not just whether there’s anyone listening, but what the public will say to intelligent life on another planet, given the opportunity.”

During Australia's National Science week – from today until 5pm Sydney time (7am GMT) on Monday 24 August – the public can visit www.HelloFromEarth.net and post 160-character text messages to the nearest known Earth-like planet.

Message in a bottle

“We’ve secured incredible support from around the globe, including NASA – people are really excited about this,” added da Silva, who spoke at the launch of the project in Canberra today.

The planet in question, Gliese 581d (pronounced 'glee-suh'), is one of more than 350 known exoplanets; which are worlds that orbit other stars.

What makes Gliese 581d special is that it’s one of the best contenders for extraterrestrial life outside our Solar System, given that it is in the habitable zone of its star. Planets in this zone are just the right distance for liquid water to potentially exist.

Eight-times the size of Earth, it is classified as a ‘super Earth’, and is the “first serious waterworld candidate,” according to one of its discoverers, Stephane Udry from the Geneva observatory in Switzerland.

COSMOS and the Australian Government, with support provided by Questacon, CSIRO and NASA, will be beaming the messages from the Canberra Deep Space Communication Complex, in Tidbinbilla, on Friday 28 August. For more information click here.

Will we get a response?

Being about twenty light-years away, the messages must travel an astounding 192 trillion kilometres at the speed of light, to arrive at Gliese 581 in around December 2029. After this, the earliest we could expect a reply is 2051, unless any aliens who receive the message have a more advanced method of sending it back to us.

At the launch of National Science Week today, in Canberra, Senator Kim Carr, the minister for innovation, industry, science and research entered the first message, which read: “Hello from Australia on the planet we call Earth. These messages express our people’s dreams for the future. We want to share those dreams with you.”

“What better way to discover the limitless possibilities of science than to give Australians the opportunity to try to seek contact with other intelligent life forms,” Senator Carr said at the launch. “As a child I, like many Australians, stared up at the stars and wondered what was out there. Now science has allowed me to send a personal message that may answer that question.

The Australian government's chief scientist, Penny Sackett, left a message which said: "Our observations indicate that your planetary system is a low-mass star orbited by at least four planets, can you confirm?"

Sending out these cosmic calls encourages us to think about "the big questions of existence," said Paul Davies of the SETI Institute and the BEYOND: Centre for Fundamental Concepts in Science at Arizona State University in the USA. These include: "what is life?", "what is intelligence?" and "what is mankind's place and destiny in the universe?"

Watch a video (left) of COSMOS editor, Wilson da Silva, and assistant editor, Jacqui Hayes, talking about the Hello From Earth project.