One of the surprising things about space exploration is that it is always surprising us.
Such was the case last week when NASA’s New Horizons probe began sending back data from Pluto, formerly our ninth planet, now considered the largest (so far) of a number of dwarf planets occupying a band of icy objects on the edge of the solar system.
Before I get to that, though, I would first like to marvel at what an accomplishment it is to send a spacecraft way out there. It is interesting that we have become so inured to space exploration that we now tend to ignore the technological feats required to engage in it.
First, Pluto is, on average, 5.9 billion kilometres away from the Earth. Its distance is constantly changing because solar orbits are elliptical. Also, in order to get the probe out there in a reasonable amount of time, scientists had to utilize the giant planet Jupiter’s gravity to “fling” it to the outer reaches.
Even so, it took nine and a half years to reach Pluto and it did so within 72 seconds of the time scientists estimated it would get there. At its closest approach, the grand piano-sized probe got within 7,800 kilometres of the dwarf planet.
That’s like launching a grain of sand and hitting a golf ball 80 kilometres distant.
And it that’s not mind-boggling enough, the flyby was very brief—the probe is travelling at approximately 50,000 kilometres per hour—meaning New Horizons had to collect a lot of data in just a few minutes.
By the time the first pictures were reaching NASA control, the spacecraft was already more than 225,000 kilometres beyond the planetoid.
Finally, consider this: the signal from New Horizons is so faint that using three 200-foot radio dishes scattered around the planet, the transmission rate is 50 times slower than a 56k modem. Imagine waiting 42 minutes to receive that selfie from a friend.
It will take 16 months for all the data to get back to us from the probe’s seven instruments.
Fortunately, scientists prioritized the data so the first thing we would get were high res photos of Pluto and its main moons. And how remarkable they were.
Scientists can be forgiven that they expected to see a inert surface pock-marked full of craters, not unlike our moon. That would have made sense. It is small (about 1/6 the size of Earth) and it is between 40 to 70 times further from the sun.
That is not what they found. The very first photo showed a vast crater-free plain that researchers estimate cannot be more than 100 million years old. In terms of the history of the solar system, Pluto’s surface is a baby.
There is also a mountain range not unlike the Rockies that appears to still be developing. We don’t know, yet, how this is possible, what source of energy could be driving it, but the fact is, Pluto is not a dead planet.
These mountains are fascinating, because they are water ice. At the temperatures on Pluto, between approximately -250C and -350C, water ice acts more like rock here on Earth.
New Horizons has also confirmed surface ice made of methane, nitrogen and carbon monoxide, all substances that are volatile gases on our planet.
Discovering new worlds is always exciting. It will be fascinating to find out more about Pluto as the data trickles in.
Charon, Pluto’s largest moon is also proving to be fascinating. New Horizons photos show a surface of deep canyons, troughs and cliffs with dark regions that also may turn out to be very youthful.
The Pluto-Charon system is also fascinating in other ways. It is unique in our solar system in that the moon does not truly orbit the planet. Both objects orbit a point that represents their mutual centre of mass. Before Charon was known, the interaction between the two actually caused scientists to vastly over-estimate the size of Pluto—it was initially thought to be approximately the same mass as Earth, which was one of the reasons it was originally classified as a planet.
However interesting Pluto turns out to be, though, it will unlikely change the decision of the International Astronomical Union to strip the status unless it changes the definition of planet.
