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
News
news

Emergency call 'started off dumb, but got pretty serious'

News
people

Britain First criticised for using actress's memory to draw attention to their 'hate-filled home page'

Arts and Entertainment
JK Rowling is releasing a new Harry Potter story about Dolores Umbridge
booksJK Rowling to publish new story set in wizard's world for Halloween
Arts and Entertainment
Benedict Cumberbatch has refused to deny his involvement in the upcoming new Star Wars film
filmBenedict Cumberbatch reignites those Star Wars rumours
PROMOTED VIDEO
News
Russell Brand was in typically combative form during his promotional interview with Newsnight's Evan Davis
people

Thought you'd seen it all after the Jeremy Paxman interview?

Arts and Entertainment
On The Apprentice, “serious” left the room many moons ago and yet still we watch
tv

Greatest mystery about the hit BBC1 show is how it continues to be made at all, writes Grace Dent

News
i100
Life and Style
tech

Voices
Funds raised from the sale of poppies help the members of the armed forces with financial difficulties
voicesLindsey German: The best way of protecting soldiers is to stop sending them into conflicts
Arts and Entertainment
A scene from David Ayer's 'Fury'
film

"History is violent," says the US Army tank commander Don "Wardaddy" Collier

News
ebooksAn unforgettable anthology of contemporary reportage
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

EBD Teacher - Food Technology Specialist

£100 - £181 per day: Randstad Education Leeds: The JobTo plan and deliver all ...

Learning Support Assistant

£50 - £60 per day + plus free travel scheme: Randstad Education Cardiff: The J...

Data Analyst/Planning and Performance – Surrey – Up to £35k

£30000 - £35000 Per Annum plus excellent benefits: Clearwater People Solutions...

Cover Supervisor

£120 - £162 per day: Randstad Education Hull: Randstad Education have cover su...

Day In a Page

Wilko Johnson, now the bad news: musician splits with manager after police investigate assault claims

Wilko Johnson, now the bad news

Former Dr Feelgood splits with manager after police investigate assault claims
Mark Udall: The Democrat Senator with a fight on his hands ahead of the US midterm elections

Mark Udall: The Democrat Senator with a fight on his hands

The Senator for Colorado is for gay rights, for abortion rights – and in the Republicans’ sights as they threaten to take control of the Senate next month
New discoveries show more contact between far-flung prehistoric humans than had been thought

New discoveries show more contact between far-flung prehistoric humans than had been thought

Evidence found of contact between Easter Islanders and South America
Cerys Matthews reveals how her uncle taped 150 interviews for a biography of Dylan Thomas

Cerys Matthews on Dylan Thomas

The singer reveals how her uncle taped 150 interviews for a biography of the famous Welsh poet
DIY is not fun and we've finally realised this as a nation

Homebase closures: 'DIY is not fun'

Homebase has announced the closure of one in four of its stores. Nick Harding, who never did know his awl from his elbow, is glad to see the back of DIY
The Battle of the Five Armies: Air New Zealand releases new Hobbit-inspired in-flight video

Air New Zealand's wizard in-flight video

The airline has released a new Hobbit-inspired clip dubbed "The most epic safety video ever made"
Pumpkin spice is the flavour of the month - but can you stomach the sweetness?

Pumpkin spice is the flavour of the month

The combination of cinnamon, clove, nutmeg (and no actual pumpkin), now flavours everything from lattes to cream cheese in the US
11 best sonic skincare brushes

11 best sonic skincare brushes

Forget the flannel - take skincare to the next level by using your favourite cleanser with a sonic facial brush
Paul Scholes column: I'm not worried about Manchester United's defence - Chelsea test can be the making of Phil Jones and Marcos Rojo

Paul Scholes column

I'm not worried about Manchester United's defence - Chelsea test can be the making of Jones and Rojo
Frank Warren: Boxing has its problems but in all my time I've never seen a crooked fight

Frank Warren: Boxing has its problems but in all my time I've never seen a crooked fight

While other sports are stalked by corruption, we are an easy target for the critics
Jamie Roberts exclusive interview: 'I'm a man of my word – I'll stay in Paris'

Jamie Roberts: 'I'm a man of my word – I'll stay in Paris'

Wales centre says he’s not coming home but is looking to establish himself at Racing Métro
How could three tourists have been battered within an inch of their lives by a burglar in a plush London hotel?

A crime that reveals London's dark heart

How could three tourists have been battered within an inch of their lives by a burglar in a plush London hotel?
Meet 'Porridge' and 'Vampire': Chinese state TV is offering advice for citizens picking a Western moniker

Lost in translation: Western monikers

Chinese state TV is offering advice for citizens picking a Western moniker. Simon Usborne, who met a 'Porridge' and a 'Vampire' while in China, can see the problem
Handy hacks that make life easier: New book reveals how to rid your inbox of spam, protect your passwords and amplify your iPhone

Handy hacks that make life easier

New book reveals how to rid your email inbox of spam, protect your passwords and amplify your iPhone with a loo-roll
KidZania lets children try their hands at being a firefighter, doctor or factory worker for the day

KidZania: It's a small world

The new 'educational entertainment experience' in London's Shepherd's Bush will allow children to try out the jobs that are usually undertaken by adults, including firefighter, doctor or factory worker