Howardites

A printable worksheet for the lesson Achondrites: rocks from melted worlds (Start here: Explorer). It prints on A4 without the website around it. The answers are on a separate sheet for the teacher.

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Start here: Explorer · Ages 10 and upHowardites worksheet

Achondrites: rocks from melted worlds

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Key words

Achondrite
An achondrite is a stony meteorite that has been melted, so it has no chondrules.
Parent body
The asteroid, moon or planet that a meteorite was originally part of before it was knocked off into space.
Basalt
A dark, fine-grained volcanic rock made mainly of pyroxene and plagioclase feldspar, found on Earth and on other worlds.
Pyroxene
A family of common rock-forming minerals made of silicon and oxygen chains, important in almost all stony meteorites.
Vesta
The second-largest object in the asteroid belt and the likely home of the howardite, eucrite and diogenite meteorites.
HED meteorites
The related family of howardites, eucrites and diogenites, thought to come from the asteroid Vesta.

Choose the right answer

Circle the letter of the right answer.

  1. Which mineral makes up most of an aubrite?
    • AEnstatite, a pyroxene rich in magnesium
    • BKamacite, an iron-nickel metal alloy
    • CGraphite, a soft black form of carbon
    • DOlivine, a green magnesium iron silicate
  2. Why are primitive achondrites seen as halfway between chondrites and achondrites?
    • AThey are made of half metal and half stone
    • BThey are full of chondrules and also of diamonds
    • CThey formed partly on Earth and partly in space
    • DThey partly melted yet kept chondrite traces
  3. A stony meteorite has no chondrules and crystallised from melted rock. Which family does it belong to?
    • AIron meteorites
    • BChondrites
    • CStony-irons
    • DAchondrites
  4. In a clay model of Vesta, where should diogenites be placed compared with eucrites?
    • AIn the metal core at the centre
    • BIn a thin layer on top of the crust
    • CDeeper, beneath the basalt crust
    • DIn the same surface lava flows
  5. Why are meteorites from the Moon and Mars counted as achondrites?
    • ABoth are still full of unmelted chondrules
    • BBoth melted and separated into layers
    • CBoth orbit the Sun inside the asteroid belt
    • DBoth are made mostly of solid iron and nickel

True or false?

Is the answer given right? Tick True or False.

  1. Some eucrites formed within about 10 million years of the Solar System's start. What does this suggest about Vesta?

    Answer given: It formed long after the planets had formed TrueFalse

  2. Why do achondrites have no chondrules?

    Answer given: Melting on their parent body destroyed them TrueFalse

Write your answer

Answer in a word or a short sentence.

  1. Why do many achondrites look like volcanic rocks on Earth?
  2. When a young asteroid melts, why does its metal end up at the centre?
  3. A meteorite comes from an asteroid that was never melted. What is it most likely to be?

Task

Make a layered model of a differentiated asteroid using modelling clay: a grey metal core, a green olivine mantle and a dark basalt crust. Cut it in half and label where irons, diogenites and eucrites would come from.

Howardites · free to copy for use in your classroom · answers are on the separate teacher's answer sheet