Juno probe heads for Jupiter from Cape Canaveral

The Atlas 5 rocket launched from Cape Canaveral Air Force Station after a brief delay caused by a helium leak

A $1.1bn (£0.7bn) unmanned Nasa space mission has launched from Florida on a journey to the planet Jupiter.

The Juno spacecraft will cruise beyond Mars to put itself in orbit around the gas giant in 2016.

It is the first solar-powered mission to venture this far from the Sun.

The mission launched atop an Atlas 5 rocket from the Cape Canaveral Air Force Station on Friday at 12:25 local time (16:25 GMT; 17:25 BST), after a brief delay caused by a helium leak.

There were concerns with the helium charging system on the rocket’s Centaur upper stage, but a small leak on the “ground side” of the rocket was found to be the culprit.

“Today, with the launch of the Juno spacecraft, Nasa began a journey to yet another new frontier,” said the agency’s administrator Charles Bolden.

“The future of exploration includes cutting-edge science like this to help us better understand our Solar System and an ever-increasing array of challenging destinations.”

Pushing boundaries

At Jupiter, where the intensity of sunlight is only 1/25th of that at Earth, space missions would normally resort to a plutonium battery.

But Juno will instead travel with three wings coated with 18,000 solar cells.

“As a solar-panelled mission, we have to keep those solar panels facing the Sun and we never go into Jupiter’s shadow,” the mission’s chief scientist Scott Bolton told BBC News.

“Those are things we can do and still accomplish our science; it doesn’t hurt us. But it would have been easier if we could have pointed just any way we wanted. We’ve had to develop [a strategy], and in fact we’ve advanced solar cell technology in doing so.”

Juno’s mission is to probe the secrets of the Solar System by explaining the origin and evolution of its biggest planet.

The spacecraft’s remote sensing instruments will look down into the giant through the many layers and measure their composition, temperature, motion and other properties.

This should yield some remarkable new insights into the coloured bands that wrap around the planet, and a new perspective on the famous Great Red Spot – the colossal storm that has raged on Jupiter for hundreds of years.

Scientists also want to measure the abundance of water in the atmosphere – an indicator of how much oxygen was present in Jupiter’s region of the Solar System when it formed.

The probe will also try to settle old arguments over whether the planet hosts a rocky core or whether its gases go all the way down to the centre in an ever more compressed state.

And it will look for the deep swirling sea of liquid metallic hydrogen that many suspect is the driver behind Jupiter’s strong magnetic field.

Juno is the second in Nasa’s so called New Frontiers class missions. The first, New Horizons, was launched towards dwarf planet Pluto in 2006 and should arrive at its target in 2015.


How Jupiter robbed Mars of mass and built the asteroid belt as the planets formed our solar system billions of years ago

Scientists have long puzzled over why Mars is only about half the size and one-tenth the mass of Earth.
As next-door neighbors in the solar system formed about the same time, they might be expected to be more similar – by rights, Mars should be as big as Earth and Venus
But a paper published this week provides an explanation and also reveals why the asteroid belt is such a strange assortment of rocks and ice.

Family portrait: Composite image of Venus, Earth and Mars shows how small the fourth planet from the Sun is in comparison with its larger siblings

While the solar system was forming, a process which began approximately 4.6 billion years ago, the gas giant Jupiter went wandering in towards the Sun, on the way dragging comets from beyond the asteroid belt as Jupiter moved inwards towards Mars.
It then moved out again to gravitate towards another gas giant, Saturn, as it formed, this time dragging dry rocks from inside the belt as it moved back outwards again.
All this material would otherwise have coalesced with Mars, giving it water in abundance and the mass to retain it with its gravitational pull.
Instead it ended up as the small, dry and probably dead planet we see today.

Dead planet: This picture taken by the Mars Exploration Rover Spirit shows the dry desolate plains that have covered the surface for eons

Dr. Kevin Walsh, a research scientist at Southwest Research Institute, in San Antonio, Texas, led an international team performing computer simulations of the early solar system.
They showed how an infant Jupiter may have migrated to within 1.5 astronomical units (AU, the distance from the Sun to the Earth) of the Sun, stripping a lot of material from the region and essentially starving Mars of formation materials.
‘If Jupiter had moved inwards from its birthplace down to 1.5 AU from the Sun, and then turned around when Saturn formed as other models suggest, eventually migrating outwards towards its current location, it would have truncated the distribution of solids in the inner solar system at about 1 AU and explained the small mass of Mars,’ said Dr Walsh.

Big bully: Composite image of Jupiter, left, and Saturn with its rings, planets which now orbit the sun far beyond the asteroid belt

‘The problem was whether the inward and outward migration of Jupiter through the 2 to 4 AU region could be compatible with the existence of the asteroid belt today, in this same region. So, we started to do a huge number of simulations.
‘The result was fantastic.
‘Our simulations not only showed that the migration of Jupiter was consistent with the existence of the asteroid belt, but also explained properties of the belt never understood before.’

Building blocks: Asteroid Lutetia and Comet Ikeya-Zhang show us what kind of material was around in the early solar system to be worked into planets by gravity

The asteroid belt is populated with two very different types of rubble, very dry bodies as well as water-rich orbs similar to comets.
Water is too volatile to have been present at Earth’s formation and must have been subsequently delivered from outer, colder parts of the Solar System .The water was probably delivered by planetoids and comets thrown out of the asteroid belt by Jupiter.
Walsh and collaborators showed that the passage of Jupiter depleted and then re-populated the asteroid belt region with inner-belt bodies originating between 1 and 3 AU as well as outer-belt bodies originating between and beyond the giant planets, producing the significant compositional differences existing today across the belt.

Red Planet: Mars, captured in the immensity of space by the Hubble telescope

The collaborators call their simulation the Grand Tack Scenario, from the abrupt change in the motion of Jupiter at 1.5 AU, like that of a sailboat tacking around a buoy.
The migration of the gas giants is also supported by observations of many extra-solar planets found in widely varying ranges from their parent stars, implying migrations of planets elsewhere in universe.
The paper, A Low Mass for Mars from Jupiter’s Early Gas-Driven Migration, appeared in the June 5 issue of the journal Nature, written by Dr Walsh, Alessandro Morbidelli of the Université de Nice, France, Sean N. Raymond of Université de Bordeaux, France; David P.O’Brien of Planetary Science Institute in Tucson, Ariz.; and Avi M. Mandell of NASA’s Goddard Space Flight Center.
The research was funded by the Helmholtz Alliance, the French National Center for Scientific Research and NASA

Read also: Jupiter’s Youthful Travels Redefined Solar System