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- 103P/Hartley 2 on Wikipedia
103P/Hartley 2
Details
103P/Hartley 2 is the small, hyperactive comet that NASA's EPOXI mission flew past in 2010, revealing a peanut-shaped nucleus barely two kilometers long with jets of carbon-dioxide gas blasting chunks of ice into space.
103P/Hartley 2 matters because it showed how vigorously a very small comet can behave. When NASA's EPOXI mission — the repurposed Deep Impact spacecraft — flew past in 2010, it found a nucleus only about two kilometers long, shaped like a peanut with a smooth waist between two rough ends. Despite its size, the comet was furiously active.
What makes Hartley 2 striking is the mechanism behind that activity. Jets of carbon-dioxide gas erupted from the rough ends, dragging fluffy chunks of water ice — some the size of golf balls, some as large as basketballs — out into the coma. This was a comet not gently sublimating but actively shedding solid pieces of itself, driven by frozen CO2 rather than water alone. The smooth waist, by contrast, appeared to be redeposited dust that had drifted back down.
That is why Hartley 2 belongs on this scale. It sits near the small end of the comets we have visited, yet it behaves more dramatically than bodies many times its size. Hartley 2 is the reminder that in the comet world, activity is set by composition and structure, not simply by how big an object is.
1.01km
Key facts
- Category
- Comets
- Object class
- Comet nucleus
- Mass
- ~300 million tonnes
- Host
- Solar System
- Scale fact
- 2.3 kmmaximum extent
- Estimated age
- ~4.5 billion years
- Composition
- Water ice, dust, frozen carbon dioxide
Scale context
Where 103P/Hartley 2 sits on the full axis
Shared physical scale
8.41km
Together, these objects make the size change around 103P/Hartley 2 easy to compare at a glance.
Sources
References for 103P/Hartley 2
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
- 103P/Hartley 2 — Wikipedia
- Visual reference: Wikimedia Commons (NASA/JPL-Caltech/University of Maryland, Public domain)
Between the smallest and the largest, perspective is everything.
About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.