Download Planets

Planets
Planets
•
Known since Babylonians:
• Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn
Planets
•
Known since Babylonians:
• Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn
Planets
•
Known since Babylonians:
• Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn
Planets
•
•
Known since Babylonians:
• Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn
… and then science happened:
Planets
•
•
Known since Babylonians:
• Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn
… and then science happened:
Planets
•
•
Known since Babylonians:
• Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn
… and then science happened:
Small Asteroids have Funny Shapes
… but Planets are Round.
… but Planets are Round.
• Gravity wants to pull everything into round shape.
• … but it has to work against friction.
• For large objects, gravity wins!
Definition of a Planet (in the Solar System)
1. A planet is in orbit around the Sun.
2. A planet is so big, it has to be round (hydrostatic equilibrium).
?
Definition of a Planet (in the Solar System)
1. A planet is in orbit around the Sun.
2. A planet is so big, it has to be round (hydrostatic equilibrium).
3. It dominates its dynamical neighborhood.
!
(Resolution 5A of the 26th General Assembly of the International Astronomical Union, 24 Aug 2006)
Dwarf Planets:
1. A dwarf planet is in orbit around the Sun.
2. A dwarf planet is so big, it has to be round.
3. It does not dominate its neighborhood (dynamically).
Pyramid-Shaped Mountain
Occator Crater
http://www.jpl.nasa.gov/dawn/world_ceres/
Water on Ceres
•
Küppers et al. (2014) observed
water vapor around Ceres.
• They used the HIFI spectrometer
onboard the Herschel Space
Telescope, engineered in
Groningen (!)
• Water evaporation is localized,
hard to tell where it’s from.
• Is it linked to bright spots???
Ceres and Water on Earth
•
Early Earth was too hot to keep water.
Yet, current Earth is dominated by deep oceans.
•
???
•
Water could be delivered from space:
• Comets
• Asteroids
•
Ceres and Water on Earth
•
Water could be delivered from space:
• Comets
• Asteroids
•
Water from comets:
• Theory seemed good at first
• But: isotope signature of water doesn’t match Earth
(see, e.g., recent Rosetta results on comet 67P).
Ceres and Water on Earth
•
Water could be delivered from space:
• Comets
• Asteroids
•
Water from asteroids:
• Asteroids like Ceres contain much water (>20% by mass)
• Isotope signature seems to match Earth’s oceans.
• Ice shouldn’t be stable on surface, only buried
underneath (?).
•
Are Ceres-like asteroids the source of water on Earth?
We’ll know better after Dawn!
Orbit Sequence
!
New Horizons Timeline
•
•
•
•
•
•
•
•
•
•
19 Jan 2006:
Launch
28 Feb 2007:
Jupiter encounter
… interplanetary cruise, mostly hibernating
6 Dec 2014:
“Wake-up call” to spacecraft
4 Jul 2015:
Spacecraft goes in “safe mode”,
problem can be fixed quickly
14 Jul 2015:
Close approach with Pluto
15 Jul 2015:
End of (scheduled!) 22-hr radio silence
thru 20 Jul:
Downlink of browse data
(with lossy compression)
thru 14 Sep:
Downlink of non-imaging data
For another year: Downlink of all, uncompressed imaging data
Credits
Credits
(Happy Birthday!)
Questions?