Death of a Pioneer

The tiny probe which boldly went where no man-made object had gone before is to be shut down in space.

In a few weeks, a rather sad ceremony will take place at one of Nasa's network of radio telescopes which tracks probes in outer space. After a few melancholy words, a scientist will tap a few keys on a keyboard instructing a computer to transmit a simple message across space.

Travelling at the speed of light from the radio telescope, the signal will flash past the moon in little more than a second. A few minutes later, it will have crossed the orbit of Mars, and, after almost four hours, it will have passed the region occupied by the most distant known planet. But its journey will be far from over. It will take nine hours for the signal to reach the tiny Pioneer 10 probe, the most distant man-made object ever sent into the cosmos.

Upon receiving the message, Pioneer 10 will do just one thing: switch itself off. A tiny voice in the immensity of space is about to fall silent forever.

Pioneer 10 was launched in 1972, with an estimated lifetime of three years. Its main mission was to reach Jupiter, the largest planet in our solar system. Before its launch, no spacecraft had travelled further than Mars. And beyond Mars, there lay what might have been an insuperable barrier to space flight: orbit upon orbit of tens of thousands of pieces of rocky debris known as the asteroid belt, which no spacecraft had yet braved.

But Pioneer 10 emerged unscathed from the asteroid belt and blazed the way to Jupiter. When it got there, it gave scientists their first close- up on the planet's kaleidoscopic display of multi-coloured clouds, detected its intense magnetic and radiation fields, and even found a thin ring of dust around the planet.

Leaving Jupiter intact was a real bonus for the scientists, as Pioneer 10's mission could now be extended to find the edge of the solar system. This was expected to be not far beyond Jupiter. The Sun gives off not just light but also a stream of particles called the solar wind. These carry with them a magnetic field, and together form a vast magnetic bubble around the Sun. This is the heliosphere, and at the time of the launch of Pioneer 10, its edge, the heliopause, was estimated to be just beyond the orbit of Jupiter.

The heliopause is an important place. Here, the Sun's influence ceases and galactic space begins. The solar wind and the material between the stars clash in a region of shock waves and turbulence. With instruments on board a spacecraft orbiting the Earth, we can look upstream to this region, in the direction of the Sun's travel through space, and see a faint glow. But week after week, month after month, Pioneer 10 did not reach the heliopause. It crossed the orbits of Saturn, of Uranus, of Neptune and tiny Pluto, yet seemed to be getting no closer to the edge of solar system space. But meanwhile, Pioneer was dying. Its tiny energy source, of radioactive plutonium-238, was fading. All but three of its 11 scientific instruments were shut down last year, and now it is down to just one - its cosmic ray detector.

Almost 9.7 billion miles away, the final goal of the most distant man- made object in the universe still remains beyond its reach. Every few days, one of the large telescopes that makes up Nasa's deep space tracking network turns towards the distant Pioneer 10 and picks up its signal - barely discernible against the background noise - from the radio transmitter, which has an output of just eight watts. It's too little for a night-light.

As it travels ever outwards at 27,800 miles per hour, its instruments are still searching for the outer boundary of the solar system; but the solar wind continues to waft past, even out in space's cold outer darkness. Faced with diminishing scientific return versus the cost of tracking it, Nasa has ordered all communications to cease on 31 March.

It is sad news, not just for the Pioneer scientists, but also for those scientists involved in scanning the sky for signals from any extraterrestrial intelligence. They have frequently used Pioneer's feeble voice to test their systems, which hope to pick up even fainter radio messages from distant civilisations. Soon they will lose their main diagnostic tool, making the search for life in space that little bit harder.

But - fate willing - the silent Pioneer 10 may still have one final task to perform as it begins its eternal drift amid the stars. On its side is a plaque inscribed with symbols, binary numbers and drawings telling of the creatures who made it. In a mere 100,000 years, it will drift past the nearest star to our solar system, a faint red star we call Proxima Centauri. From then on, who knows what other stars it will visit? It will still be somewhere among the stars long after our Sun and the Earth are gone, and possibly long after mankind is just a memory.

After Pioneer 10 is closed down by a signal from Earth, who knows if the next signal it receives will be from someone, or something, else? Who knows what they will make of this primitive space probe? Pioneer 10 could be what mankind is judged by

The writer is the BBC's science correspondent

Suggested Topics
Start your day with The Independent, sign up for daily news emails
New Articles
tvDownton Abbey Christmas special
Arts and Entertainment
Wolf (Nathan McMullen), Ian (Dan Starky), The Doctor (Peter Capaldi), Clara (Jenna Coleman), Santa Claus (Nick Frost) in the Doctor Who Christmas Special (BBC/Photographer: David Venni)
tvOur review of the Doctor Who Christmas Special
News
peopleIt seems you can't silence Katie Hopkins, even on Christmas Day...
News
news
PROMOTED VIDEO
News
i100
Arts and Entertainment
Left to right: Stanley Tucci, Sophie Grabol and Christopher Eccleston in ‘Fortitude’
tvSo Sky Atlantic arrived in Iceland to film their new and supposedly snow-bound series 'Fortitude'...
Arts and Entertainment
Jenna Coleman as Clara Oswald in the Doctor Who Christmas special
tvForget the rumours that Clara Oswald would be quitting the Tardis
Arts and Entertainment
Japanese artist Megumi Igarashi showing a small mascot shaped like a vagina
art
News
The Queen delivers her Christmas message
newsTwitter reacts to Her Majesty's Christmas Message
Arts and Entertainment
tv
Life and Style
fashion
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Account Manager

£20000 - £35000 per annum: Recruitment Genius: This full service social media ...

Recruitment Genius: Data Analyst - Online Marketing

£24000 - £35000 per annum: Recruitment Genius: We are 'Changemakers in retail'...

Austen Lloyd: Senior Residential Conveyancer

Very Competitive: Austen Lloyd: Senior Conveyancer - South West We are see...

Austen Lloyd: Residential / Commercial Property Solicitor

Excellent Salary: Austen Lloyd: DORSET MARKET TOWN - SENIOR PROPERTY SOLICITOR...

Day In a Page

A Christmas without hope: Fears grow in Gaza that the conflict with Israel will soon reignite

Christmas without hope

Gaza fears grow that conflict with Israel will soon reignite
After 150 years, you can finally visit the grisliest museum in the country

The 'Black Museum'

After 150 years, you can finally visit Britain's grisliest museum
No ho-ho-hos with Nick Frost's badass Santa

No ho-ho-hos with Nick Frost's badass Santa

Doctor Who Christmas Special TV review
Chilly Christmas: Swimmers take festive dip for charity

Chilly Christmas

Swimmers dive into freezing British waters for charity
Veterans' hostel 'overwhelmed by kindness' for festive dinner

Homeless Veterans appeal

In 2010, Sgt Gary Jamieson stepped on an IED in Afghanistan and lost his legs and an arm. He reveals what, and who, helped him to make a remarkable recovery
Isis in Iraq: Yazidi girls killing themselves to escape rape and imprisonment by militants

'Jilan killed herself in the bathroom. She cut her wrists and hanged herself'

Yazidi girls killing themselves to escape rape and imprisonment
Ed Balls interview: 'If I think about the deficit when I'm playing the piano, it all goes wrong'

Ed Balls interview

'If I think about the deficit when I'm playing the piano, it all goes wrong'
He's behind you, dude!

US stars in UK panto

From David Hasselhoff to Jerry Hall
Grace Dent's Christmas Quiz: What are you – a festive curmudgeon or top of the tree?

Grace Dent's Christmas Quiz

What are you – a festive curmudgeon or top of the tree?
Nasa planning to build cloud cities in airships above Venus

Nasa planning to build cloud cities in airships above Venus

Planet’s surface is inhospitable to humans but 30 miles above it is almost perfect
Surrounded by high-rise flats is a little house filled with Lebanon’s history - clocks, rifles, frogmen’s uniforms and colonial helmets

Clocks, rifles, swords, frogmen’s uniforms

Surrounded by high-rise flats is a little house filled with Lebanon’s history
Return to Gaza: Four months on, the wounds left by Israel's bombardment have not yet healed

Four months after the bombardment, Gaza’s wounds are yet to heal

Kim Sengupta is reunited with a man whose plight mirrors the suffering of the Palestinian people
Gastric surgery: Is it really the answer to the UK's obesity epidemic?

Is gastric surgery really the answer to the UK's obesity epidemic?

Critics argue that it’s crazy to operate on healthy people just to stop them eating
Homeless Veterans appeal: Christmas charity auction Part 2 - now LIVE

Homeless Veterans appeal: Christmas charity auction

Bid on original art, or trips of a lifetime to Africa or the 'Corrie' set, and help Homeless Veterans
Pantomime rings the changes to welcome autistic theatre-goers

Autism-friendly theatre

Pantomime leads the pack in quest to welcome all