How long till you can send e-mail to Mars?
June 3, 2001
NEW YORK To reach colonists on Mars, you might attach "mars.sol" to the e-mail address. For retrieving images from one of Jupiter's moons, a file transfer from a "europa.sol" site might be in order.
The space missions making that possible may be years or lifetimes away, but initial steps toward extending the Internet's reach are already in the works.
The first component, a short-range transceiver, hitched a ride on the Mars Odyssey, which was launched in April and is due to reach the Red Planet in October.
As envisioned, an internet on Mars could connect various surface landers and orbiting satellites. Additional internets could appear elsewhere, all linked to form a giant Interplanetary Internet.
And techniques for extending networks into the remote reaches of outer space could ultimately prove useful for extending the current Internet into remote regions on Earth.
Researchers, who released a 58-page proposal in mid-May, scheduled workshops during meetings of the Internet Society in Stockholm this coming week.
Deploying all the hardware could take decades. But then again, the Internet on Earth has taken 31 years to build, and is still under construction.
"You have to start somewhere," said Vinton Cerf, an Internet founding father and adviser to the space project. "For many of us, the idea of building an Interplanetary Internet sounds like Fantasyland, but it's straightforward engineering. It's stuff we know how to do."
Adrian Hooke, the project's manager, said the Interplanetary Internet would expand one component at a time, primarily by hitching rides on spacecraft built for other projects: "It's a never-ending process, just as the way the Earth's Internet has evolved."
The concept is still on the drawing boards, though, with no timetable or even a formal commitment at the National Aeronautics and Space Administration. Hooke, who works at NASA's Jet Propulsion Laboratory, expects key scheduling decisions this year.
NASA now has a Deep Space Network of three radio dishes on Earth scanning for signals from its spacecraft. The Interplanetary Internet would standardize components so that spacecraft could talk to one another, instead of only to Earth.
Remember the Mars Pathfinder lander and its rover, Sojourner? The rover took more than 500 pictures from the Mars surface and communicated with the lander using customized protocols. But from there, the images went directly to Earth.
With the Interplanetary Internet's standardized protocols, the lander could have beamed signals to an orbiting satellite from a previous mission. Satellites, which generate more power than surface landers, could then amplify the signal. That ultimately means more pictures with better quality.
Or take a spacecraft exploring the outer planets. It could pass images and data through satellites along the way. At each stop, the satellite could request retransmissions of any data lost in transit.
Either way, though, NASA would still have to post images and data to computers on Earth for public viewing. Distances and other resource constraints won't make it practical for space buffs to directly request pages from a Web server on Mars.
Standards would, however, let NASA reuse its components and share access with other countries, scientists or even commercial space ventures.
The international Consultative Committee for Space Data Systems has already been working for 20 years to standardize links between satellites and the ground. More than 150 missions worldwide use them. The Interplanetary Internet adds relaying capabilities.
The radio transceiver now whizzing to Mars at a relative 65,000 mph is intended as the first relay for future landers.
Space agencies from other countries have also expressed interest in adding equipment.
"We are very conscious that this is a very sensible way to move ahead," said Peter Allan, who heads the United Kingdom's delegation to the space standards group.
Initially, the Interplanetary Internet could transmit images and such data as atmospheric and surface conditions. It could also let mission controllers send commands to spacecraft.
Commercial applications, such as mining asteroids, could follow in decades to come.
"There's a strong incentive to develop plug-and-play space infrastructure," NASA's Hooke said. "This is funded on public money, so it ought to be opened up to a wider audience."
It's a similar approach to the Earth's Internet. Begun as a research project, the Internet ultimately grew to include commercial ventures, which came up with new uses.
In fact, the interplanetary project received more than $500,000 from the U.S. Defense Advanced Research Projects Agency, the same government agency that financed the Net's early development.
There are many differences, though.
The Earth's moon and a space shuttle may be close enough to run off Earth's Internet. But farther out, the project envisions separate internets, perhaps one for each planet or an interplanetary spaceship in transit.
By keeping the networks separate, engineers avoid having to make service calls to Mars to keep up with technological advances on Earth. And they won't have to constantly send to Mars a dot-com database containing more than 20 million names and counting.
The Interplanetary Internet would also use different communications protocols.
On Earth, the Internet's glue is TCP/IP, a standard way for disparate networks to recognize one another. But the technique requires constant connections -- something not practical when a message takes 15 to 45 minutes to reach Mars and back.
And because of planet rotation and orbit, guaranteeing a constant connection would be difficult even without the delay.
Project researchers have come up with an alternate protocol called bundling. It works like e-mail; if your computer is off, the message sits on a server until the next time you log on.
Cerf, who led a team that invented the TCP/IP protocols in the 1970s, said he has been thinking about the Internet's next step for some time.
"It's exciting," he said. "It's like living in a science fiction story. You don't know exactly how it will come out, but you know you're doing something special."
By ANICK JESDANUN, Associated Press