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Hubble Observations
of Main Belt Comets
or “Active Asteroids”
Max Mutchler
Space Telescope Science Institute
Baltimore, Maryland
Hubble Science Briefing
6 February 2014
The Extraordinary Multi-tailed Main-belt Comet P/2013 P5
Jewitt, David; Agarwal, Jessica; Weaver, Harold;
Mutchler, Max; Larson, Stephen
The Astrophysical Journal Letters, Vol. 778, Issue 1 (2013)
Overview
• This is not our parents asteroid belt! And not the one of
movies and video games either…
• The asteroid belt is more dynamic than imagined a
generation ago
– Main Belt Comets
– A bigger role in the mystery of Earth’s oceans?
• Related discoveries: Ceres, Europa water vapor
2
Asteroids:
typically rocky, with
circular orbits
between Mars
and Jupiter…
Main Asteroid Belt
3
Comet orbit
Comets:
typically a mixture of
Main Asteroid Belt
ices and rock, with
elliptical orbits extending
to the outer Solar
System
4
Video about Main Belt Comets with Star Wars clip!
http://www.youtube.com/watch?v=qchvgRUDUzA
5
6
Citation from IAU Minor Planet Circular 56612 on the naming of
Asteroid “6815 Mutchler”
7
Asteroid history and mystery
• Ceres, Vesta, Pallas,
discovered in early 1800s
• Called planets for 50
years, then re-classified:
any déjà vu ?
• Key to understanding
Solar System formation
…and us
• Giveth: our oceans?
• Taketh away: Killed the
dinosaurs? Still a threat?
• Exploration with Hubble,
Dawn…and astronauts?
8
Star (and planetary system) formation
in the Carina Nebula – see the jets?
Credit: NASA, ESA, and M. Livio and the
Hubble 20th Anniversary Team (STScI)
9
Star (and planetary system) formation
in the Carina Nebula – see the jets?
Credit: NASA, ESA, and M. Livio and the
Hubble 20th Anniversary Team (STScI)
10
Artists impression of a protostar forming: asteroids are leftover
planetesimals from this era – the beginning of the Solar System
Credit: NASA/JPL-Caltech/R. Hurt (SSC)
11
Most of the debris left over from planet-building was
ejected from the Solar System
Credit: NASA
12
The “Nice Model” for the dynamical
history of the Solar System
R. Gomes, Hal Levison, Alessandro Morbidelli and Kleomenis Tsiganis, 2005, Nature, 435
a)
b)
c)
Simulation showing the outer planets and planetesimal belt:
a) early configuration, before Jupiter and Saturn reach a 2:1 resonance
b) scattering of planetesimals into the inner Solar System after the
orbital shift of Neptune and Uranus
c) after ejection of planetesimals by planets.
13
Late Heavy Bombardment
Image Credit: Julian Baum
14
After the Earth cooled off, later asteroid and comet impacts
may have delivered water and organic material to Earth
– the stuff of life.
Image credit: Don Davis / NASA
Image credit: Don Davis / NASA
15
But does the water add up?
http://ga.water.usgs.gov/edu/earthhowmuch.html
Credit: Howard Perlman, USGS;
globe illustration by Jack Cook,
Woods Hole Oceanographic
Institution (©); Adam Nieman.
16
Water Ice Discovered on Asteroid for First Time
By Clara Moskowitz
SPACE.com Senior Writer
28 April 2010
Water ice has been found on the surface of a nearby asteroid for the first
time – a discovery that could help explain how Earth got its oceans.
Two teams of researchers independently verified that the asteroid 24
Themis – a large rock hurtling through space in the asteroid belt between
Mars and Jupiter – is coated in a layer of frost. They also found that the
asteroid contains organic material, including some molecules that might
be ingredients for life.
The discovery might even provide clues about the origin of water on
Earth. “Our data are certainly at least consistent with the idea that you
could bring in plenty of water from impacts”, said Andrew Rivkin of Johns
Hopkins University.
17
A comet in the asteroid belt?
Nope!
18
Images Credit: NASA, ESA, and D. Jewitt (UCLA)
“A recent disruption of the main-belt asteroid P/2010 A2”
David Jewitt, Harold Weaver, Jessica Agarwal, Max Mutchler & Michal Drahus
Nature, Volume 467, 14 October 2010
http://hubblesite.org/newscenter/archive/releases/2010/34/
19
Illustration by
Ann Feild, STScI
20
Research by William F. Bottke, David Vokrouhlicky and David
Nesvorny suggests that the impactor believed to have wiped out
the dinosaurs and other life forms on Earth 65 million years ago
can been traced back to a breakup event in the main asteroid belt.
21
Asteroid Scheila:
a “Main Belt Comet” ?
In the wee hours of December 11, 2010,
University of Arizona astronomer Steve Larson
was on cosmic patrol with the Catalina Sky
Survey's Schmidt telescope. That's when he
noticed something odd about the appearance of
the main-belt asteroid 596 Scheila. The
asteroid was clearly fuzzy, with a soft glow
extending a few arcminutes to the west and
north. Other astronomers quickly confirmed the
cometary appearance. If Scheila is truly a longdormant comet, then it's a big one: current
estimates put its diameter at 70 miles (113 km).
"It's a main-belt comet, although I don't know
what type yet," Dave Jewitt explains. He says it
could have resulted from an impact (as
occurred earlier this year with P/2010 A2) or
outgassing (as occurs on 133P/Elst-Pizarro).
http://www.skyandtelescope.com/news/112140939.html
Credit: S. Larson and A. Gibbs (University of Arizona/Catalina Sky Survey)
22
23
Artists’s impression of a smaller asteroid colliding with much bigger asteroid Scheila:
not all collisions were billions of years ago!
http://hubblesite.org/newscenter/archive/releases/2011/13/
24
“different causes
for different
objects: impacts,
rotational breakup,
and sublimation”
Asteroids, Comets, Meteors
2012, Niigata, Japan.
LPI No. 1667, id.6152
25
26
http://hubblesite.org/newscenter/archive/releases/2013/52/
27
The YORP effect: solar radiation spinning
up irregularly-shaped small asteroids, and
causing mass loss for the “rubble piles”? 28
Artist’s impression: Herschel detects water vapor
emanating from Ceres!
http://www.esa.int/Our_Activities/Space_Science/Herschel/Herschel_discovers_water_vapour_around_dwarf_planet_Ceres
29
Artist’s impression: Herschel detects water vapor
emanating from Ceres!
http://www.esa.int/Our_Activities/Space_Science/Herschel/Herschel_discovers_water_vapour_around_dwarf_planet_Ceres
30
Google hangout about Hubble observations of Vesta and Ceres for the Dawn mission:
http://dawn.jpl.nasa.gov/dawncommunity/Google_hangout_12_05_2013.asp
31
dwarf planet
asteroid
(small solar system body)
Google hangout about Hubble observations of Vesta and Ceres for the Dawn mission:
http://dawn.jpl.nasa.gov/dawncommunity/Google_hangout_12_05_2013.asp
32
Why does roundness matter ?
Image credits: Gaspra, Ida: Galileo (NASA/JPL);
Vesta and Mars images: HST (NASA/STScI);
Eros: NEAR Shoemaker (JHU/APL)
Mars
33
Why does roundness matter ?
Vesta’s impact crater
NASA, ESA, and A. Feild (STScI)
Computer model: Credit: NASA/ESA
34
Dawn
Ceres
2015
Vesta
2011
Image: William K. Hartmann Courtesy of UCLA
35
This graphic shows the location of water vapor detected over Europa's south pole that
provides the first strong evidence of water plumes erupting off Europa's surface.
Hubble didn't photograph plumes, but spectroscopically detected auroral emissions
from oxygen and hydrogen. The aurora is powered by Jupiter's magnetic field. The
image of Europa is derived from a global surface map generated from Voyager and
Galileo observations.
NASA/ESA/L. Roth (Southwest Research
Institute and University of Cologne, Germany)
Science Credit: NASA, ESA, L. Roth (Southwest Research Institute and University of Cologne, Germany), J. Saur (University of
Cologne, Germany), K. Retherford (Southwest Research Institute), D. Strobel and P. Feldman (Johns Hopkins University),
M. McGrath (Marshall Space Flight Center), and F. Nimmo (University of California, Santa Cruz)
36
This is an artist's concept of a
plume of water vapor thought to
be ejected off of the frigid, icy
surface of the Jovian moon
Europa, located 500 million miles
from the Sun.
Hubble Space Telescope
spectroscopic measurements
lead scientists to calculate that
the plume rises to an altitude of
125 miles and then probably
rains frost back onto the moon's
surface. Previous findings
already point to a subsurface
ocean under Europa's icy crust.
Artwork Credit: NASA, ESA, and K. Retherford
(Southwest Research Institute)
37
This is an artist's concept of a
plume of water vapor thought to
be ejected off of the frigid, icy
surface of the Jovian moon
Europa, located 500 million miles
from the Sun.
Hubble Space Telescope
spectroscopic measurements
lead scientists to calculate that
the plume rises to an altitude of
125 miles and then probably
rains frost back onto the moon's
surface. Previous findings
already point to a subsurface
ocean under Europa's icy crust.
Artwork Credit: NASA, ESA, and K. Retherford
(Southwest Research Institute)
… fish added by Max!
38
Hubble observations of Main Belt Comets or "active asteroids"
Since 2010, a series of Hubble observations has been conducted to help characterize a
recently discovered class of Solar System objects known as Main Belt Comets. These objects
can be more accurately described as “active asteroids” -- they have circular orbits in the Main
Asteroid Belt, but they appear to exhibit comet-like activity. A recent observation revealed an
asteroid sprouting six tails! Along with discoveries of frosty asteroids, and water vapor
emanating from the largest asteroid Ceres, there is the tantalizing possibility that Main Belt
Asteroids can help explain how Earth's oceans formed.
Max Mutchler has been working on the entire Hubble mission -- almost 24 years -- and is
currently the head of the Research and Instrument Analysis Branch at the Space Telescope
Science Institute. Max is an expert on Hubble’s cameras, and has been involved in a wide
range of scientific observations with them. As a member of the Hubble Heritage team, he has
helped produce many of the iconic images that Hubble is famous for. In particular, Max loves
the challenge of observing Solar System objects with Hubble. He is a member of the team that
has discovered four moons of Pluto in support of the New Horizons mission, and he has also
worked with the Dawn mission to observe Vesta and Ceres with Hubble.
Hubble press release and Google Hangout with Dave Jewitt covering 6-tailed asteroid “P5”:
http://hubblesite.org/newscenter/archive/releases/2013/52/
http://www.youtube.com/watch?v=CGgRNWUFfZ0
39
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