New Horizons Mission To Pluto Fran Bagenal University of Colorado Compared to Earth at 1AU what is the flux of sunlight at 33 AU? Pluto orbits the Sun every 248 years 2 nd Kuiper Belt object discovered 1992 Pluto was discovered in 1930 by Clyde Tombaugh at the Lowell Observatory, Arizona Pluto now Pluto is sometimes closer to the Sun than Neptune - is it an escaped moon of Neptune? Orbital calculations show Pluto and Neptune s orbits to be in 3:2 resonance Tombaugh spent many nights at the telescope, many days looking at photographic plates - looking for objects that move relative to the stars Modern Kuiper Belt Object Detection Digital Image Comparison Sample Kuiper Belt Objects The second object in the Kuiper Belt was detected in 1992. Now there are 1000s of Kuiper Belt Objects - KBOs Parallax motion Thousands of them and Varied 1
Slicing the solar system by natural categories Jovian planets Terrestrial planets Main-belt asteroids Near-Earth asteroids Jupiter trojans Centaurs Kuiper Belt objects 1000 km Asteroid Belt 1000 miles Ceres A Moon, Charon! Why is discovery of a moon so valuable? 1978 Even with a good telescope, the Earth s atmosphere makes tiny Pluto look very fuzzy Looking Sideways View From Earth Late 1980s Mass: 1/8 : 457 : 1 Earth at same scale Mutual Eclipses Pluto's moon Charon Pluto Pre-decisional Binary Planet 2
Spin-Orbit Phase Lock Pluto & Charon both spin and orbit every 6.4 days This is the very, very best we can do from Earth... including Hubble Space Telescope Density ~ 2g/cc 50:50 rock:ice Charon Pluto Temperature: 40 Kelvin -233 Celsius -390 F Surface = Ice +...??? 1988 Star occulted by Pluto Po~3-50 microbar, T~50K Quick Time-Out to discuss: - Where did these icy objects come from? - Why care about Pluto & Kuiper Belt? Collapse of the Solar Nebula Rocks & Metals Ices + Rocks & Metals Frost Line 3
Asteroid Belt What's missing from this simple story? Kuiper Belt Not so simple... How long did it take to make the planets? Make small rocky planets close to the Sun Make giant planets with lots of hydrogen surrounding large ice cores Nebula collapse <1 Million Year planetesimal formation in 1MY Jupiter, Saturn < 2 MY Earth, Venus, Mars <4 MY Uranus & Neptune? Hard to make U & N at present orbits Where did earth s oceans come from? How to make Kuiper Belt? Exo-planets imply Migration But it s not so simple Planet migration Over past ~15 years ideas of solar system formation have been changing Jupiter & Saturn Neptune & Uranus Numerical model Planetesimals Scattering of planetesimals building blocks of planets From Hal Levison, Catherine Kretke, Southwest Research Institute, Boulder CO Jupiter Saturn Uranus Neptune Puts Uranus & Neptune in their current orbits In 1989 we started planning a mission to Pluto Scatters planetesimals into the Kuiper Belt Delivers water to the Earth Finding what Pluto a Kuiper Belt Object is like will test out these ideas 4
After many NASA commitees, studies, starts, stops... SWAP Rex PEPSSI 2001: Proposing Eyes & Ears Lorri 2005: Testing Ralph Alice 2004: Building SDC New Horizons - Student Dust Counter SDC counts dust particles. Where does the dust come from? Getting Ready for Launch In the meantime... Pluto Charon Hubble Space Telescope finds 4 more moons! Hydra Nix Kerberos Styx SIX OBJECTS TO STUDY 5
Launch Day! January 19, 2006 The 9.5 year journey Charon- Earth Occultation 14:20:09 15:00 Pluto-Earth Occultation 12:52:30 Hydra Moving at 33,000 mph! How long does it take the radio signal to get from New Horizons at 33 AU to Earth at 1AU from the Sun? Charon- Sun Occultation 14:17:50 Pluto-Sun Occultation 12:51:28 14:00 13:00 12:00 Charon C/A 12:04:00 Pluto C/A 29,432 km 11:50:00 13,695 km 13.78 km/s Nix 11:00 0.24 Sun Earth 10 mins New Horizons Trajectory 33 AU x 8 min / AU = 264 min = 4.4 hr Preprogrammed Choreographed Dance of Observations http://eyes.nasa.gov/ But New Horizons is busy collecting data...... it takes 4.5 hours to communicate to Earth... and send down the data at a rate of 3 kb/s... What's the data rate on your cell phone? New Horizons is a Robot! So... we had to wait. 6
What did we do while waiting for the data to come down? We took selfies! July 20, 1969 July 14, 2015 Finally Alice Bowman (Mission Operations Manager MOM) announces the spacecraft is well and full of data! The New Horizons team has lots of women! And we all go nuts! Breath-taking! Complex Ice World with a Heart! We get a clear view of the side we fly past fuzzier on the other side Remember... Pluto's 6.4 spin period and 2 hours to fly past MOON 7
Given it's size and density what do you expect for internal structure & surface geology? H 2 O CO CH 4 N 2 Ice, Ice, Ice! Thin layer liquid water? Density =1.86 g/cc 1/3 Ice 2/3 Rock Density =2 g/cc 50:50 Ice & Rock CO Ices cover N 2 younger areas H 2 O Fresh snow? Seasonal changes? Water Ice in older areas Covered with black stuff?! CH 4 Water Ice Acting like Rock Icebergs? Oblique impact crater filled with N 2 ice? Convecting N 2 Sputnik Planitia Sputnik Planitia 1335 x 1025 km Where does heat come from to drive convection? Topographic Map McKinnon et al. Nature 8
Pluto's weak gravity produces a puffed out atmosphere Atmosphere absorbs solar UV light Haze! Aerosols Photochemical reactions Bigger & Bigger Molecules Ethylene (C 2H 4) Acetylene (C 2H 2) Rains out onto surface https://www.youtube.com/watch?v=q6xzpjkl8du Cthulhu Older, darker more cratered Tholins Photolysis products of N 2, CH 4, CO Tombaugh Regio Younger, brighter crater free tholins Increasing time > Darkens 9
Light/dark layers - suggesting episodic formation and deposition?? Methane Ridges?? 10 km 6.2 miles 500 km 300 miles Are Pluto's pits similar to these terrestrial features but grown much bigger over millions of years? 33 km 20 miles What are these features??!! Pluto's Pits 10
Even Charon has complex geology 40 miles ~ 70 km No Atmosphere for Charon! Kerberos What do you see? How did it get that way?...not synchronous! Spin Period Body Days Orbits Pluto 6.387 1 Charon 6.387 1 Styx 3.239 6.22 Nix 1.829 13.6 Kerberos 5.33 6.04 Hydra 0.4295 88.9 New Horizons Mission Trajectory???? What's Next?? 11
Kuiper Belt & Pluto Launch Jan 2006 Dec 31 2018 / Jan 1 2019 Why have we seen few objects in these 2 directions? The Milky Way! Our Galaxy gets in the way too many stars! Jupiter Saturn Uranus Neptune Pluto 2,400 km 1,400 miles Pluto Pluto July 2015 40 km 25 miles KBO 2014 MU69 "Ultima Thule" 100 km Small Astroids & Comets MU69 What did NASA s New Horizons mission to Pluto cost per person in US? A. $100B / 300M = $300 / person B. $10B / 300M = $30 / person C. $1B / 300M = $3 / person D. $100M / 300M = 30c / person E. $10M / 300M = 3c / person After M. Brown, 2013 12