Pluto Shows Its Heart in New Image from NASA

Pluto Shows Its Heart in New Image from NASA

The latest image of Pluto taken by NASA’s New Horizons spacecraft shows a heart-shaped feature on the surface.  The photo was taken last night and transmitted back to Earth just before it turned to face Pluto for its closest encounter, which took place at 7:50 am Eastern Daylight Time (EDT) this morning.  The spacecraft will turn back to Earth and resume transmitting data at 8:53 pm EDT tonight – an anxiously awaited “phone home” transmission that will tell mission managers that all is well.

New Horizons has been sending back data about Pluto for weeks that is “better than Hubble” — better than what can be observed using the Hubble Space Telescope in Earth orbit — and the latest image is the sharpest yet of the surface of Pluto.   Once the 9th planet in the solar system, it was redesignated as a “dwarf planet” by the International Astronomical Union in 2006, though many people, including New Horizons Principal Investigator (PI) Alan Stern and NASA Administrator Charlie Bolden, still call it a planet. 

Image of Pluto taken by NASA’s New Horizons spacecraft on July 13, 2015 Eastern Daylight Time.  Image credit NASA.

Scientists do not yet know what surface characteristics are creating the heart-shaped feature.  Higher resolution data that the spacecraft took today and will begin sending back to Earth tomorrow hopefully will solve that mystery.  The spacecraft was intended to come as close as 7,750 miles (12,472 kilometers) from Pluto’s surface, but data from the spacecraft already revealed that the planet is slightly larger than expected.  Stern said that meant they came 70 kilometers (43 miles) closer.

The spacecraft and Pluto are 3 billion miles (4.9 billion kilometers) from Earth and it takes 4.5 hours for a radio signal to travel that distance at the speed of light, meaning a 9-hour two-way signal travel time.   In the early phases of this closest approach to Pluto, the spacecraft’s antenna along with its instruments were pointed at Pluto so data could not be sent back to Earth. In the later phases underway now, it has turned back this way, but is busy collecting science data looking at Pluto’s atmosphere, in particular, from the far side back towards the Sun. 

Once it has completed those scientific measurements, it will resume transmissions to Earth.  That moment — the “phone home” signal — is at 8:53 pm EDT tonight.  NASA’s next televised media briefing begins at 8:30 pm EDT and lasts through that critical moment.

Because of data rate limitations, the first signal will be only a 15 minute burst of engineering data revealing the spacecraft’s health.  Science data will follow.   NASA and the project’s scientists have prioritized what data to return first since it will take a total of 16 months to return all the data that was collected.   The maximum data rate is 4 kilobits per second according to Alice Bowman, mission operations manager at the Johns Hopkins University’s Applied Physics Lab (APL) in Laurel, MD.  APL built and operates the spacecraft for NASA.

Yesterday, Stern and Deputy PI Cathy Olkin cautioned against making snap judgments about what they think they may be seeing in the images and other data.  Stern repeated that today when asked if the surface features reveal evidence of tectonics.  “I’m not sure, is the honest answer,” he replied, because the data need to be properly processed and studied.

Stern was asked again about the possibility that the spacecraft might have encountered debris as it passed by Pluto with mission-ending consequences.  He again downplayed that possibility (although yesterday he said it was a 1 in 10,000 possibility and today he said 2 in 10,000).   No one will know for sure until 8:53 pm EDT tonight.

To guard against such a possibility, though, the spacecraft collected and sent back to Earth “fail safe” data sets before the black-out period.  We have “obviously revolutionized knowledge” about Pluto already, Stern said, but stressed that 99 percent of the data are still on the spacecraft and there would be “great disappointment” if it was lost.

Stern noted that exactly 50 years ago today, NASA’s Mariner 4 spacecraft made the first successful flyby of Mars and it is “fitting today that we complete the exploration of the planets.”

Correction: Two typos were corrected regarding the distance to the spacecraft and Pluto: they are 3 BILLION miles (4.9 BILLION kilometers from Earth).

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