New Horizons: Pluto shows its spots to Nasa probe

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http://www.bbc.com/news/science-environment-33369045

[h=1]New Horizons: Pluto shows its spots to Nasa probe[/h]By Jonathan Amos BBC Science Correspondent

• 2 July 2015
  
• From the section Science & Environment

The science team on the American New Horizons mission to Pluto has released two colour views of the dwarf planet and its biggest moon, Charon.

They were made by combining pictures from the probe’s high-resolution, “black and white” camera, Lorri, and its lower-resolution, colour imager known as Ralph.
The difference in hue between Pluto and Charon is clear.

But what catches the eye are four dark spots on the 2,300km-wide dwarf planet.

Each spot is about 500km across. Quite why they should be so similar in size and spacing is not clear.

Their dominant placing is on the hemisphere that New Horizons will not see during its close flyby on 14 July.


However, there should be ample opportunity to study them in the days leading up to the encounter.

“It’s a real puzzle - we don’t know what the spots are, and we can’t wait to find out,” said New Horizons principal investigator, Alan Stern, of the Southwest Research Institute.

“Also puzzling is the longstanding and dramatic difference in the colours and appearance of Pluto compared to its darker and greyer moon Charon.”

If, as scientists think, Pluto and Charon are the products of a collision between two primitive bodies in the early Solar System, one might expect them to look more similar.

New Horizon’s flyby data will hopefully provide the answer.

The US space agency (Nasa) mission is now closing in on Pluto and its five moons.

The moment of closest approach on the 14th will take place at 11:49 GMT, when the probe is just 12,500km above the surface.

It is moving too fast - at 13.7km/s - to go into orbit, and it will simply scream past the dwarf and its satellites, gathering as much data as it can.

No pictures will be sent back to Earth on the day itself; the spacecraft will be too busy executing its pre-programmed observation campaign.

Instead, the first images from the flyby should be presented on the following day, on 15 July.

Controllers have decided not to alter the course of the probe.

They had been looking for icy debris in the vicinity of Pluto that might pose a collision hazard, but could find nothing obvious.

New Horizons was commanded to make a thruster burn earlier this week, to speed it up ever so slightly.

This will ensure the spacecraft reaches a precise point in space and time to carry out the pre-programmed observation sequence.

The probe must spin around to take pictures of all the different targets, and if its navigation is off by even a small amount it will be looking in the wrong direction at the critical moment.

On Thursday, New Horizons was just under 15 million km from Pluto, but 4.7 billion km from Earth.

The vast distance to the probe's home world means a radio signal takes about 4.5 hours from sending to receipt.

The BBC will be screening a special Sky At Night programme about Pluto on Monday 20 July, which will recap all the big moments from the New Horizons flyby.

[email protected] and follow me on Twitter: @BBCAmos

 

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[h=1]New Horizons: Nasa spacecraft speeds past Pluto[/h]By Jonathan Amos BBC Science Correspondent, Laurel, Maryland

• 51 minutes ago
  
• From the section Science & Environment

Nasa's New Horizons spacecraft has made the first visit to Pluto, speeding past at 14km per second.
Earlier, the space agency released the most detailed picture yet as it hurtled towards the dwarf planet on Tuesday.
The probe was set to grab more pictures and other data as it passed 12,500km from Pluto at 11:50 GMT (12:50 BST).
Controllers got a last health status report, before the robotic craft turned its antenna away from the Earth to concentrate on its target.

We have completed the initial reconnaissance of the Solar SystemAlan Stern, New Horizons chief scientist​

Only when New Horizons has its trove of images safely in its onboard memory will it call home again.






This is not expected to happen until just after midnight (GMT) into Wednesday.
It means there will be a long, anxious wait for everyone connected with the mission, as they hold out for a signal that will be coming from almost five billion km away.
But scientists already have colour data from the approach and said they might release a new picture later on Tuesday. Images set to be released on Wednesday will be more than 10 times the resolution of those already published.
New Horizons' flyby of 2,370km-wide Pluto is a key moment in the history of space exploration.

The robotic probe turns its antenna away from Earth during the flyby "We have completed the initial reconnaissance of the Solar System, an endeavour started under President Kennedy more than 50 years ago and continuing to today under President Obama," said the mission's chief scientist Alan Stern.
"It's really historic what the US has done, and the New Horizons team is really proud to have been able to run that anchor leg and make this accomplishment."

"This is true exploration...that view is just the first of many rewards the team will getJohn Grunsfeld, Nasa science chief​

It marks the fact that every body in that system - from Mercury through to Pluto - will have been visited at least once by a space probe.
"This is true exploration...that view is just the first of many rewards the team will get. Pluto is an extraordinarily complex and interesting world," said John Grunsfeld, Nasa's science chief.
The information acquired on approach will be as nothing to the huge number of observations it will have acquired during the flyby. But scientists have already been attempting to interpret the data and images so far.

Dr Stern said: "On the surface we see a history of impacts, we see a history of surface activity in terms of some features we might be able to interpret as tectonic - indicating internal activity on the planet at some point in its past and maybe even in its present."
"This is clearly a world where geology and atmosphere - climatology - play a role. Pluto has strong atmospheric cycles, it snows on the surface, these snows sublimate - go back into the atmosphere - every 248-year orbit."
The probe will investigate not only Pluto but also its five moons: Charon, Styx, Nix, Kerberos and Hydra.
To achieve that, it had to perform a furious set of manoeuvres as it pointed every which way in the sky to get the images and other types of data it needs.

[h=2]Analysis - David Shukman[/h]

David Shukman talks to Al Tombaugh, the son of Pluto discoverer Clyde The cheering and jubilation are phenomenal. There's a powerful sense of achievement at sending a robotic craft three billion miles to Pluto. But there's also something much more instinctive: the thrill of witnessing and sharing a great moment of discovery.
Most moving for me has been catching a few words with the son of the man who first found Pluto. Al Tombaugh is obviously delighted that a sample of his father Clyde's ashes is on board New Horizons speeding past Pluto and now heading into the unexplored realm of the Kuiper Belt.
I asked Al if his father would have wanted to visit the tiny world. Maybe, he said, but he was always worried about the physical strain of life as an astronaut. Another thought that's very striking here today: so many scientists and engineers and technicians have had a hand in making this mission work, and their excitement is totally justified.
So what about the coming hours? No one here will truly relax until the next signals reach home as the spacecraft slips beyond Pluto.

Because the observations are all run on an automated command sequence, New Horizons had to fly a perfect path past Pluto, and with perfect timing - otherwise its cameras would have shot empty sky where the dwarf or its moons were expected to be.
This necessitated aiming New Horizons at a "keyhole" in space just 100km by 150km (60miles by 90 miles), and arriving at that location within a set margin of 100 seconds.
The last indications were that New Horizons was on the button of that aim point, being perhaps 70km closer to the surface of Pluto than anticipated, and arriving about 72 seconds early.
All this was achieved after a multi-billion-km flight across the Solar System lasting nine-and-a-half years.
The mission team will not celebrate until New Horizons contacts Earth again, which should happen at 00:53 GMT Wednesday (01:53 BST).
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Media caption Prof Alan Stern says Pluto is "a little larger than anticipated"

This communication will contain only engineering information on the status of the probe, but controllers should be able to tell very quickly whether the flyby sequence worked properly or not.
The first high-resolution pictures from the pass should be downlinked later on Wednesday.
There is a very small possibility that New Horizons could be lost as it flies through the Pluto system.
Any stray icy debris would have been be lethal if it had collided with the spacecraft at its 14km/s velocity (31,000mph).
"Hopefully it did [survive]," said Alan Stern, "but there is a little bit of drama."
On Monday, the New Horizons team announced a new, more precise measurement of Pluto's diameter at 2,370km. The probe sees the girth of Charon to be very similar to earlier estimates, at 1,208km.

How Pluto and its biggest moon, Charon, compare in size to the Earth The BBC will be screening a special Sky At Night programme called Pluto Revealed on Monday 20 July, which will recap all the big moments from the New Horizons flyby.
Follow Jonathan on Twitter.