Opening new doors in space
It was in 1980 that John Anderson first wondered if something funny was going on with gravity. The Jet Propulsion Laboratory physicist was looking over data from two Pioneer spacecraft...
Los Angeles Times
It was in 1980 that John Anderson first wondered if something funny was going on with gravity.
The Jet Propulsion Laboratory physicist was looking over data from two Pioneer spacecraft that had been speeding through the solar system for nearly a decade.
Only something was off base. The craft weren't where they were supposed to be.
In fact, rather than traveling at a constant velocity of more than 25,000 mph toward the edge of the solar system, Pioneer 10 and 11 inexplicably were slowing down. Even factoring in the gravitational pull of the sun and the other planets couldn't explain what he was seeing.
How could that be?
At first, Anderson figured there must be a simple explanation. Maybe there was a malfunction on board the spacecraft. Maybe his calculations were wrong.
"I assumed something was going on that I didn't understand," said Anderson, 70. "So I just kept at it."
Two decades later, Anderson's work on what is now called the Pioneer Anomaly may be paying off.
In October, a European Space Agency panel recommended a space mission to determine whether Anderson had found something that could rewrite physics textbooks. Some cosmologists even speculate the Pioneer Anomaly might help unravel some of the thorniest problems in theoretical physics, such as the existence of dark matter or mysterious extra-dimensional forces predicted by string theory.
Whether Anderson will be remembered as the man who changed history or the guy who spent decades of his life chasing an illusion, all that's clear at this point is that he will be remembered.
For the record, gravity is one of the most closely studied forces in the universe.
Sir Isaac Newton first measured it in the 17th century. Every object in the universe attracts every other object, Newton determined, with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. That means the bigger things are, and the closer they are, the greater their gravitational pull.
In 1915, a former Swiss patent clerk named Albert Einstein refined the theory, arguing that gravity occurs when planets or stars warp the fabric of space around them, just as a bowling ball on a trampoline warps the surface of the trampoline. Instead of a sucking force, Einstein's general theory of relativity said, small objects fall toward larger ones like a marble rolling down the slope of the trampoline to the bowling ball.
Einstein's theory has been successfully tested again and again. Without it, complex space missions such as Pioneer 10 and 11 would have ended in disaster, either by missing their targets — in this case, flybys of Jupiter — or by crashing.
Anderson already was an experienced space hand when the Pioneers were launched in 1972 and 1973. Having worked on Mariner missions in the 1960s, he was chosen to be principal investigator for gravity research on both Pioneer missions.
It would prove to be a surprisingly long ride. The TRW-built Pioneers performed so well that after the initial two-year mission ended, the National Aeronautics and Space Administration decided to send them on a new mission to explore the solar system's outer planets.
They were the first spacecraft to travel through the asteroid belt, which some scientists at the time thought could be as dangerous as a field of icebergs. Pioneer 10 was first to pass the orbit of Pluto. For many years, until overtaken by the speedier Voyager 1, the Pioneers were the farthest-venturing human-made objects in space.
By 1980, the vehicles were still zipping through space in fine shape — when Anderson stumbled upon the unexpected.
"I started plotting this anomalous acceleration toward the sun," Anderson said. In space-science-speak, that meant the spacecraft were improbably slowing down.
To be sure, the anomaly was small. It amounted to about 8,000 miles a year, a fraction of the 219 million miles the spacecraft covered annually. The anomaly is about 10 billion times weaker than Earth's gravity.
But inches and meters add up. After nearly 30 years, the difference is about 248,000 miles, the distance from Earth to the moon.
Anderson, ever the cautious scientist, didn't tell anyone what he was seeing for a decade. Early on, the probes still were so close to the sun that he reasoned radiation and solar wind could be affecting them.
The other possibility was a spacecraft "systematic": an onboard mechanical problem. Prime suspects were gas leaks, along with releases of energy by the plutonium-powered radioisotope thermoelectric generators that provided electric power to the instruments.
None of these candidates seemed capable of producing errors as large as Anderson was charting.
There was one piece of evidence that seemed to support the idea that the anomaly could be real: It was almost exactly the same on both spacecraft. On the other hand, both Pioneers were built by the same company to identical specifications, so why shouldn't the same problem show up on both?
As years passed, and the Pioneer probes moved away from the sun's influence, the anomaly didn't disappear — or change.
Anderson was stumped. He began burrowing deeper into the numbers.
He still was scratching his head when physicist Michael Martin Nieto at the Los Alamos National Laboratory in New Mexico called one day in 1994 looking for material for an upcoming speech about new developments in physics.
"Well, I've got this thing with Pioneer," Anderson said.
"I almost fell off my chair," Nieto said.
That's when, for good or ill, the Pioneer Anomaly went public. As word spread in the scientific world, critics appeared. This can't be right, they said. You have a software error. You're not interpreting the data correctly. And there were the usual off-center enthusiasts who were convinced the researchers had found proof of aliens, God or both.
A key ally
Anderson's work attracted another group, led by former Soviet scientist Slava Turyshev, the first Soviet scientist to leave his country for a job with the JPL.
Although never funded by NASA to work on the anomaly, Turyshev plunged into the project as a volunteer, eventually becoming the Pioneer Anomaly's door-to-door salesman. He traveled Europe seeking support for a space mission that could solve the riddle.
"This is a form of space archaeology," he said.
The first sign that the world's space bureaucracy was taking notice occurred in 1995, when NASA gave the research team a $247,000 grant to pay for an independent analysis of the Pioneer data. The Aerospace Corp. in El Segundo, Calif., was chosen.
"They came back and said, 'Guys, you have something here,' " Turyshev said.
In 2002, Anderson, Turyshev, Nieto and other team members published the most detailed analysis of the Pioneer Anomaly. The dense, 54-page paper, which appeared in the peer-reviewed journal Physical Review, considered every conceivable space event: effects of solar radiation and solar wind, the force of radio beams used to communicate with Earth, gas leaks, helium leaks and gravity from the Kuiper Belt, a region beyond Neptune that contains Pluto and a number of small, planetlike objects.
They even looked at whether ocean tides might affect NASA's Goldstone Deep Space Network facility, where Pioneer's radio transmissions were received. Although Goldstone was many miles from the shore in the Mojave Desert, it rested on California's geologic Pacific plate. So, the team factored in the remote possibility that waves hitting the beaches were ever-so-slightly jiggling instruments at Goldstone.
Nothing came close to explaining the anomaly.
What are implications?
"There are two possible explanations," Turyshev said. "The most plausible is systematics."
The second possibility is new physics.
"If it's new physics, the implications are truly tremendous," he said.
One possibility is that dark matter is holding the spacecraft back. Some cosmologists believe dark matter exists because only 10 percent of the expected mass of the universe has been found. If 90 percent of the universe's mass and energy is invisible, maybe it could exert gravitational pull on spacecraft.
Another possibility, even more fanciful, is that invisible dimensions are tugging at the Pioneers. This idea has its origin in string theory, a two-decade-old school of thought that suggests we are surrounded by more than the three dimensions we know about. Some versions of string theory suggest there could be as many as 11 dimensions, most of which are curled up and hidden from us.
A third possibility is that gravity has been hiding secrets that three centuries of research have failed to uncover.
Anderson and his colleagues have known for some time that the only way to prove the anomaly is to duplicate the Pioneer Anomaly with another spacecraft.
First, they considered other NASA missions that penetrated the outer solar system, finally settling on the 1989 Galileo and 1990 Ulysses.
Although some data appeared to show the anomaly had affected them, results were not conclusive enough for Turyshev and Anderson.
A natural candidate was the twin Voyager missions, launched in 1977. The Voyagers' meanderings offered plenty of space far out of reach of the sun for the anomaly to show up, but their orienting technology was so different that the data were useless.
The only solution was a new space mission. But NASA wasn't interested.
High-flown theoretical physics involving relativity had a more ready reception in Europe. So Turyshev hit the road.
Down the road ...
In October, the team was excited to learn that the Fundamental Physics Advisory Group had recommended a European Space Agency mission to study the Pioneer Anomaly. That was the good news. The not-so-good news was that the launch wouldn't happen before 2015, and the answer to the anomaly might not come back for decades.
It's unclear how many of the Pioneer team will be around to greet the new data. But if the anomaly turns out to be real, the story will be as much, if not more, about grinding persistence as the flash of insight that is supposed to be the badge of genius.
"Some have told us the most impressive thing was that we wouldn't be stopped," Nieto said. "We just keep going."
Anderson never has permitted himself to hope he might have found something that could change the way people think about the cosmos.
"I used to think the probability of making a fundamental discovery was pretty remote," Anderson said. "Now, I kind of wonder about it."
Whatever the solution to the Pioneer Anomaly, it will be reached without any more help from the Pioneers. NASA lost contact with Pioneer 11 in 1995. Pioneer 10's last message came in January 2003.
Sam and Sara Lucchese create handmade pasta out of their kitchen-garage adjacent to their Ballard home. Here, they illustrate the final steps in making pappardelle pasta.