Comets, giant asteroids, dwarf planets. Welcome to 21st century space exploration.
http://photojournal.jpl.nasa.gov/catalog/PIA17650
DAWN spacecraft, powered by an Ion Thrust Drive, on its way to dwarf planet Ceres, deep in the asteroid belt. https://gregole.com/2015/01/27/mission-to-the-asteroid-belt-codename-dawn/
It just got the best-ever image of dwarf planet Ceres: 
NASA DAWN Mission photo
How big is Ceres?
Ceres (minor-planet designation1 Ceres) /ˈsɪəriːz/[17] is a dwarf planet located in the asteroid belt, which lies between the orbits of Mars and Jupiter. It is composed of rock and ice, is 950 km (590 mi) in diameter, and contains a third of the mass of the asteroid belt. It is the largest asteroid and the only dwarf planet in the inner Solar System. http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29
“Ceres Earth Moon Comparison” by CWitte – This picture was composed from Image:Mercury_Earth_Comparison.png, Image:Full Moon Luc Viatour.jpg, and Image:Ceres_optimized.jpg by –CWitte 11:33, 26 July 2007 (UTC). Licensed under Public Domain via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Ceres_Earth_Moon_Comparison.png#mediaviewer/File:Ceres_Earth_Moon_Comparison.png
Comets. 67P Churyumov-Gerasemenko is being orbited and closely monitored by the European Space Agency Rosetta space craft. But where is that thing? Here’s a handy link to keep track of its location: http://www.livecometdata.com/comets/67p-churyumov-gerasimenko/
We are discovering more about the forbidding little mini-world everyday. And it looks very cool: 
http://sen.com/news/rosetta-s-comet-reveals-it-is-full-of-surprises
And what we are learning about 67P CG are raising more questions than providing answers. I like that. That’s when we progress with our knowledge:
http://sen.com/news/rosetta-s-comet-adds-to-the-riddle-of-earth-s-oceans
The first published results from the Rosetta space mission since it went into orbit around a comet have thrown a spanner in the works for scientists trying to understand where Earth’s water came from.
Vapour given off by Comet 67P/Churyumov-Geramisenko show that its water is very different in character from that covering our own planet.
A leading theory to explain the Earth’s oceans has been that the water was delivered from space by heavy bombardment by comets in the distant past…- See more at: http://sen.com/news/rosetta-s-comet-adds-to-the-riddle-of-earth-s-oceans#sthash.8UFRoixW.dpuf
The conjecture has been that comets formed in the Kuiper belt in the vicinity of Uranus and Neptune were far enough away from the sun that they retained their water content and were even flung out into the Oort cloud by gravitational interactions with Jupiter. Once they slowly re-entered the outer solar system from the Oort cloud, some of these frozen, forbidding bodies of weird stuff we call comets, were then hurled into the inner solar system by Jupiter’s mighty gravitational field and bombarded the early Earth enough to fill up the oceans.
Hmmm. Proving this has been tough:
Deuterium/hydrogen (D/H) ratio in other comets have shown a wide range of values. Of the 11 comets for which measurements have been made, only the Jupiter-family Comet 103P/Hartley 2 was found to match the composition of Earth’s water. Meteorites from the Asteroid Belt also match the composition of Earth’s water.
Though asteroids have a lower water content, impacts by a large number of them could still result in Earth’s oceans…- See more at: http://sen.com/news/rosetta-s-comet-adds-to-the-riddle-of-earth-s-oceans#sthash.8UFRoixW.dpuf
Read the link to get the importance of the D/H ratio matching Earth water and comet water – as you can see, they haven’t matched up too well. Wait a minuet. Couldn’t the water have come from asteroids; and aren’t we about to visit the biggest one in the asteroid belt? Oh. It has water! Lots of it. Let’s check its D/H ratio!
And this link has a lot of great 67P CG photos and info:
http://rosetta.jpl.nasa.gov/gallery/images/comet-67p/churyumov-gerasimenko
This link is indispensable – just mesmerizing – and you can see the amazing job the European space jocks did with gravitational assists and complex orbital mechanics. Too bad they didn’t have enough common sense to equip the lander with a nuclear battery!
Alan Olee Book Report 
And there was this close encounter with a binary asteroid! http://www.nasa.gov/jpl/asteroid-that-flew-past-earth-today-has-moon/index.html#.VMvPaC5BnwB
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