Read the rule before answering
Check both the object and its classification: this asks for a terrestrial planet, not just an object with a rocky surface. A moon or dwarf planet does not qualify.
Six untimed questions, starting with this one.
Check an answer here
Check this question’s accepted set without submitting to a game or opening the full answer list.
Only your submitted spelling will be checked. Other answers stay hidden.
Read the lesson — reveals answers & strategy
Understand the boundary
Terrestrial planets have solid surfaces. This set contains Mercury, Venus, Earth and Mars. “Rocky” describes a type of planet; it does not admit every rocky object. A moon, asteroid or dwarf planet remains outside this four-planet set.
Verify the facts: NASA · Our solar system ↗
Choose an answer for your goal
Mercury earns 69 fixed points here, Venus 56, Mars 20 and Earth 15. Those gaps are editorial choices, not measured differences in how often people remember them. Mercury is the highest-scoring choice in this edition; Mars is quicker to type. Choose between a score target and an input you can confidently finish before the deadline. Repeating a correct answer never changes its fixed score.
Worked examples — reveals answers
- Mercury · Accepted
- A terrestrial planet and a member of this exact four-answer set.
- Pluto · Outside this set
- A dwarf planet; having a solid surface does not satisfy this planet classification.
- Moon · Outside this set
- Earth’s natural satellite is not a planet.
Practice the distinction
Before opening the list, name the four inner planets in order. Check one answer below. Then switch to the outer-planet question and explain why the same answer would fail there.
Try it in the checker ↑Give me a hint — no answer revealed
Start with the full category, then apply the exact boundary: One of the four terrestrial planets. You only need one qualifying answer. A longer name is not automatically rarer.
Reveal a verified practice pick
This pick belongs to the selected question’s answer set. Points are a fixed knowledge rating.
Reveal a fast high-scoring answer
Shortest accepted input at 65+ points
MercuryMercury · 69 points · 7 characters
Mercury is planet 1 from the Sun. Dwarf planets are a separate classification.
Highest fixed score
Mercury69 points · Shortest accepted spelling: Mercury
These are editorial points, separate from real player choice counts.
Reveal all 4 practice answers
Filter by a name or listed alias. Scores are fixed knowledge ratings.
4 accepted answers
No answers match these filters. Try another spelling or a lower minimum score.
What players actually choose
– UTC · 660 recorded daily rounds. Source: Krillion io daily submissions. Skips and timeouts are included in the denominator; practice and Battle are excluded.
576 / 660 rounds ended with an accepted answer (87.3%). Average: 36.0 fixed points.
Compare observed choices — reveals answers
Question quality signals
These measurements cover completed daily rounds recorded with timing and rejection details. Older rounds without those fields are excluded. At least 20 measured rounds are required per question.
Review thresholds: below 20% accepted, at least 40% timed out, or at least 30% of rounds with an unlisted input. These flags suggest checking the wording and answer coverage; they do not prove an answer is wrong or change points automatically. Abandoned rounds and practice attempts are not included.
How these statistics work
- What is counted
- Source: Krillion io daily submissions. Skips and timeouts count as rounds; practice and Battle are excluded.
- When comparisons appear
- A question needs at least 20 recorded rounds. An answer also needs at least 5 recorded choices within that question.
- What the data can tell you
- These anonymous browser records are not verified unique people or a representative survey. The player rarity index does not change game points or predict the original Krillion game. Raw submissions stay private.
Rule examples & common mix-ups — may reveal answers
- The eight planets and dwarf planets are separate sets. A moon belongs to neither planet set; apply any size, position or name-length condition as well.
These notes explain the question boundary; they are not a ranking of player mistakes.
Why these answers qualify
Each entry belongs to the bounded set defined by the prompt. The named source supports the underlying facts; our editorial scoring is a separate layer.
Source: NASA · Our solar system ↗
Reference version: 2026-09-13. See our answer policy for how we handle aliases and omissions.