Unit 2: Probability of Life Elsewhere

Anchor Phenomenon

4.5 billion years passed and 5 mass extinctions occurred before intelligent life evolved on Earth. Does life — or intelligent life — exist somewhere else?

Unit Driving Question

Does life exist somewhere outside Earth? What about intelligent life? Why haven’t we made contact?

Unit Overview

So far, we’ve found no evidence of life anywhere else in the universe. But the universe is unimaginably vast — there are more stars than grains of sand on Earth, and most stars have planets. In this unit, you investigate the conditions that allowed life to evolve on Earth, from the stability of our solar system to the coevolution of life and Earth’s atmosphere, and use that understanding to argue whether intelligent life likely exists elsewhere.

Performance Expectations

Standard	Description
HS-ESS1-2	Construct an explanation of the Big Bang theory based on astronomical evidence of light spectra, motion of distant galaxies, and composition of matter in the universe
HS-ESS1-4	Use mathematical or computational representations to predict the motion of orbiting objects in the solar system
HS-ESS1-6	Apply scientific reasoning and evidence from ancient Earth materials, meteorites, and other planetary surfaces to construct an account of Earth’s formation and early history
HS-ESS2-5	Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes
HS-ESS2-7	Construct an argument based on evidence about the simultaneous coevolution of Earth’s systems and life on Earth

Lesson Sequences

Chapter	Topic	Days	Standards
Opening	Anchor phenomenon, initial models, driving question board	2	—
Stability of the Solar System 5E	Craters, asteroid impacts, water properties, rock cycle	7–8	HS-ESS1-6, HS-ESS2-5
Coevolution of Earth & Life 5E	Fossil record, oxygen history, feedbacks, extinction events	7–8	HS-ESS2-7
Origin of the Universe 5E	Redshift, Big Bang, cosmic background radiation, galaxy formation	6–7	HS-ESS1-2
Asteroid Orbits 5E	Apophis, Kepler’s Laws, gravity, planetary defense	5–7	HS-ESS1-4
Closing	Performance task: probability of intelligent life elsewhere	1–2	All

What You’ll Figure Out

By the end of this unit, you will be able to:

☄️ Explain why Earth has so few craters compared to the Moon and Mars
🦠 Construct an argument about how life and Earth’s systems coevolved over 4 billion years
🌌 Model the origin of the universe using evidence from light spectra and cosmic expansion
🪨 Predict asteroid orbits using mathematical representations of gravity
🛡️ Evaluate solutions for planetary defense against asteroid impacts
📢 Argue whether intelligent life likely exists elsewhere in the universe

# Unit 2: Probability of Life Elsewhere {.unnumbered} ## Anchor Phenomenon > **4.5 billion years passed and 5 mass extinctions occurred before intelligent life evolved on Earth. Does life — or intelligent life — exist somewhere else?** ## Unit Driving Question > **Does life exist somewhere outside Earth? What about intelligent life? Why haven't we made contact?** ## Unit Overview So far, we've found no evidence of life anywhere else in the universe. But the universe is unimaginably vast — there are more stars than grains of sand on Earth, and most stars have planets. In this unit, you investigate the conditions that allowed life to evolve on Earth, from the stability of our solar system to the coevolution of life and Earth's atmosphere, and use that understanding to argue whether intelligent life likely exists elsewhere. ## Performance Expectations | Standard | Description | |----------|-------------| | **HS-ESS1-2** | Construct an explanation of the Big Bang theory based on astronomical evidence of light spectra, motion of distant galaxies, and composition of matter in the universe | | **HS-ESS1-4** | Use mathematical or computational representations to predict the motion of orbiting objects in the solar system | | **HS-ESS1-6** | Apply scientific reasoning and evidence from ancient Earth materials, meteorites, and other planetary surfaces to construct an account of Earth's formation and early history | | **HS-ESS2-5** | Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes | | **HS-ESS2-7** | Construct an argument based on evidence about the simultaneous coevolution of Earth's systems and life on Earth | ## Lesson Sequences | Chapter | Topic | Days | Standards | |---------|-------|------|-----------| | **Opening** | Anchor phenomenon, initial models, driving question board | 2 | — | | **Stability of the Solar System 5E** | Craters, asteroid impacts, water properties, rock cycle | 7–8 | HS-ESS1-6, HS-ESS2-5 | | **Coevolution of Earth & Life 5E** | Fossil record, oxygen history, feedbacks, extinction events | 7–8 | HS-ESS2-7 | | **Origin of the Universe 5E** | Redshift, Big Bang, cosmic background radiation, galaxy formation | 6–7 | HS-ESS1-2 | | **Asteroid Orbits 5E** | Apophis, Kepler's Laws, gravity, planetary defense | 5–7 | HS-ESS1-4 | | **Closing** | Performance task: probability of intelligent life elsewhere | 1–2 | All | ## What You'll Figure Out By the end of this unit, you will be able to: - ☄️ **Explain** why Earth has so few craters compared to the Moon and Mars - 🦠 **Construct** an argument about how life and Earth's systems coevolved over 4 billion years - 🌌 **Model** the origin of the universe using evidence from light spectra and cosmic expansion - 🪨 **Predict** asteroid orbits using mathematical representations of gravity - 🛡️ **Evaluate** solutions for planetary defense against asteroid impacts - 📢 **Argue** whether intelligent life likely exists elsewhere in the universe