Planetary Interior - Enceladus

We are off to Space! Put yourself In planetary scientists' shoes!

Planetary Interiors Presentation (JHU)

Audience: Kids (elementary school to high school)

Goals:

• show that scientific fields are fascinating and fun :)
• create an interactive presentation where audience goes at their own pace
• present very important scientific concepts in a fun way

"Dream": share this presentation with you, the department, with colleagues to build on it and share it with schools

Unfold the solar system mysteries

Detective

Universe - Galaxies

Moment of Inertia

Solar System

Gravitational Field

Planets

Magnetism

Moons

Target of interest!

Planetary Science

Let's discover more about Where we are living

Understand the relation between Earth, Solar System, Galaxies, Universe :)

From the Universe to Galaxies

Universe refers to the entirety of all physical matter and energy, solar systems, planets, galaxies, and all contents of the space. Universe includes all celestial objects.

A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems. Our galaxy, the Milky Way, also has a supermassive black hole in the middle. When you look up at stars in the night sky, you're seeing other stars in the Milky Way.

Solar System

• The solar system consists of the Sun, planets, moons, asteroids, meteors, comets, dust, gases, and empty space.

The milky Way

• Our solar system exists inside a collection of solar systems called the "Solar Neighborhood".
• Our solar system is inside the Milky Way galaxy which is one of hundreds of millions, possibly billions of galaxies that make up the universe!

Feeling small yet?

The SUN

The Sun is enormous compared to the Earth!

Guess how many Earth(s) could fit in the Sun?

The Sun creates a lot of gravity because it is huge.

The Sun's gravity holds several planets in their orbits as they circle around the Sun. How many planets orbit around the Sun?

The Sun is a star. A star does not have a solid surface, it is a ball of gas held together by its own gravity.

Planets

What are the names of the 8 planets orbiting the Sun?

Planets are heavenly bodies, revolving around the Sun in elliptical orbits.

There are 2 main groups of planets:- the inner planets (or terrestrial planets) - the outer planets (or gas planets)

Inner vs Outer planets

The inner planets, also called terrestrial planets are:

• close to the Sun
• small and dense
• made of rock and metal
• slow rotation
• few moons
• weak / no magnetic field

The outer planets, also called gas planets are:

• far to the Sun
• big and low density
• made of gas
• fast rotation

• many moons
• strong magnetic field

Earth has The Moon, what about other Planets?

Moons are large pieces of rock that orbit around a planet. Our Moon isn't the only one. Most planets in our solar system have moon(s).

Moons come in many shapes, sizes, types. Some have atmospheres and even hidden oceans beneath their surfaces.

Let's discover the moons of our solar system planets!

Moons in our Solar System

Mercury: 0Venus: 0 Earth: 1 Mars: 2 Jupiter: 79 Saturn: 82 Uranus: 27 Neptune: 14

Can Life exist on a Moon?

In order for a moon to be hospitable to life, it must have an atmosphere, water, and oxygen. It must also have acceptable temperature that does not vary too much over time.

2 candidates:Jupiter's moon Europa Saturn's moon Enceladus

What is Planetary Science?

Planetary science is the scientific study of planets and their planetary systems which includes moons, ring systems, gas clouds, and magnetospheres. It is a cross-discipline field!!

Astronomy

Atmospheric Science

Geology

Biology

Chemistry

Space Physics

Discover the main questions planetary science tries to answer!

Discover the main tools planetary scientists use!

MAIN Planetary Bodies Properties

SIZE

COMposition

MASS

Rotation

Orbit

Planetary Scientist - being sherlock holmes!

Planetary scientists are like crime scene detectives!

Analyze evidence

to uncover information about what happenedPS analyze data from probes and rovers to understand the geological and atmopheric processes of other planetary bodies!

Attention to detail

require an eye for detail and meticulous approach to analysis. PS carefully study images and data to identify patterns and anomalies

Deductive reasoning

to make sense of the evidence they collect. PS formulate hypotheses about the processes that shaped other planetary bodies

Let's discover some of planetary science clues

Moment of Inertia

MOI is the quantity expressed by a body resisting angular acceleration. It can be written as: I = m r^2 m: the mass of the body r: the distance from axis of rotation MOI is the opposition from a body that is under rotation due to the torque. MOI of a rigid body does not change with the speed of rotation.

MoI for planetary science

The MOI of a planet gives information about how the planet's mass is distributed around its axis of rotation. A planet with a larger MOI will rotate more slowly than a planet with a smaller MOI because a larger MOI planet means that its mass is distributed further away from its axis of rotation. It makes it harder to spin.

The MOI of a planet provides insights about the planet's internal structure. Scientists can infer the density distribution and the state of the core (liquid, solid)

Gravitational Field

A gravitational field is a model used to explain the influence that a massive body has. This influence extends into the space around itself, producing a force on bodies around.

The gravitational field can be visualized as a 3d space around the object. The strength of the gravitational force at any points depends on the object's mass and the distance from it.

The gravitational field of planets help us better understand the internal structure or planets. Click here to know more about planetary applications!

Gravitational Field

Asymmetries in the gravitational field give us information about the internal structure. If there is a large asymmetry in the gravitational field, it may suggest that the mass distribution within the planet is not symmetric. This could be due to the presence of a dense core, or by variations of density in the mantle or in the crust.

Magnetism

Magnetism is an invisible force caused by the unique properties of certain materials. In most objects, electrons spin in different, random directions. This causes them to cancel each other out over time. In magnets the molecules are uniquely arranged so that their electrons spin in the same direction. This arrangement of atoms creates two poles in a magnet, a North-seeking pole and a South-seeking pole.

Today's target of interest

Today's goals

• Put yourself in Sherlock Holmes' shoes and observe

• Through first impressions we will get some suggestions about Enceladus' internal structure

• Quick story about Cassini's results to better understand how fascinating Enceladus is!

Paper:

• what do we learn from first impressions: shape, how it looks like
• what do we learn from gravity and MoI
• what do we learn from librations
• play with 2-layer model to fit the MoI values

First impression

Very small world (diameter ~ 500 km)

Smaller worlds have a harder time retaining heat (bc more surface area per volume than larger worlds)

Enceladus could fit within the length of the United Kingdom

First impression

Very far from the Sun (Saturn barely receives 1/100 of sunlight compared to Earth)

Not a lot of heat coming from the Sun

"For a moon that size, we expected it to be frozen solid" (Spilker)

First impression

The whitest object in the solar system (bond albedo = 0.81 compared to Earth's = 0.3)

surface nearly pure, pristine water ice (only thing that can be that reflective which also suggested a young surface)

Cassini revelations

Before Cassini, Enceladus was thought to be like many objects in our SS: cold, small, well outside the habitable zone

“Enceladus was interesting, But no one knew just how interesting until Cassini got there.”

With Cassini, Enceladus became one of the the best places beyond Earth to search for conditions suitable for past or present life.

Launched in 1997 Ended (grand finale) in 2017

Cassini Cameras

Cassini cameras spied linear features near the South pole, that had different color than the rest of the icy surface.

--> suggested that they might be relatively young

Cassini Cameras

Cassini cameras show South pole to be nearly free of craters

--> suggested that the surface is very young (craters are a sign of how old objects are)

Most of Saturn’s moons are heavily cratered. At Enceladus, things hace erased them:

• something melting and filling in
• something that covers the craters

Enceladus Temperatures

Equator (most direct sunlight): -316 F (-193 C)

South Pole (should be colder): -307 F (-188 C)

Tiger stripes (linear fractures): -261 F (-163 C)

==>

30 C warmer than equator

(Credit: NASA)

Enceladus is no dead world. It is active!

Enceladus' "Plumes"

Warm enough to allow small reservoirs of water Water would be shoot up through cracks and spray out like geysers --> "plumes"

All these jets came from the 4 tiger stripes!

Ion and Neutral MS (INMS) analyzed particles and gases in the plume:

water vapor, carbon dioxide, carbon monoxide, organic materials!

(Credit: NASA/JPL)

Enceladus seems to have subsurface water reservoirs!Later, other arguments proved a global ocean!

Enceladus & Saturn

Enceladus is tidally locked to Saturn

(same side of the moon always faces the planet)

--> the moon spins on itself at the same rate it orbits Saturn

No perfect circular orbit, but very small eccentricity (e = 0.0047)

--> very subtal wobble movement also called librations!

--> tell about the interior (if solid body or if crust is floating on an ocean)

Enceladus could not wobble so much if the shell and the wore were solidly connected. It has a global ocean!

Enceladus - Why do we Care?

Geysers / Plumes eruptions

Plumes of water vapor and icy particles erupt at the south pole of the moon's surface. Study the interior without having to land on it

Potential for Life

Scientists believe that there is liquid water (a key ingredient for life as we know it). A potential subsurface ocean beneath its icy crust. The ocean might be in contact with the moon's rocky core (source of energy to support microbe life?)

Planetary Decadal Survey

Enceladus is listed as one of the main target of interest with the proposed Flagship mission "Orbilander"!

Thank you!

Please feel free to contribute to this ongoing presentation

Cassini Science

Illustration from the Cassini Grand Finale (Credit: NASA/JPL-Caltech)

Scientists also found what appeared to be a surprisingly dense cloud of water vapor and ice grains over the south pole.Flybys helped scientists confirm earlier suspicions that Enceladus is the main source of material for Saturn’s E ring.

Enceladus

(Ruggieri et al., 2018)

Enceladus

is an active body (Cassini Mission)

resurfaced, areas with no craters --> geologically young

(Porco et al., 2006)

systems of ridges, fractures, grooves --> tectonically altered surface

newly discovered dark spots --> maybe venting of subsurface volatiles

presence of an atmosphere --> presence of geologic activities (if not a sublimated atmosphere would be lost due to small size + weak gravity)

(Hansen et al., 2006)

elevated temperatures at south polar region + source of water vapor and ice particles

(Spencer et al., 2006)

These observations require a degree of endogenic activity, supporting the hypothesis of a differentiated body

Tiger stripes!