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Planetary Magnetism. How crucial is a planet’s magnetic field?. Relative sizes of Earth and Mars. Shape of their magnetic fields. Earth. Mars. Mars’s crust has small pockets with magnetic fields. The rest is unprotected many harmful effects from the Sun.

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Presentation Transcript
slide1

Planetary Magnetism

How crucial is a planet’s magnetic field?

slide3

Relative sizes of Earth and Mars

Shape of their magnetic fields

Earth

Mars

slide4

Mars’s crust has small pockets with magnetic fields.

The rest is unprotected many harmful effects from the Sun.

Magnetized rocks in the crust create these fields

slide6

Where does Earth’s magnetic field come from?

It’s complicated, but simply put: its outer core. Movement of electrically conducting fluid creates the geodynamo.

slide7

Earth

A global magnetic field helps to protect a planet’s atmosphere from the harmful effects of the Sun’s magnetic field and solar wind.

Mars

slide9

Many scientists think that Mars might have had a stronger global magnetic field billions of years ago, when water once flowed on its surface.

It may have looked like this:

slide10

So where did Mars’s atmosphere go?

We think that magnetism has a lot to do with it, but we still don’t completely understand

How is NASA continuing to study this?...

slide12

The End

Unless you really want to know more….

science summary
Science Summary
  • Mars’s atmosphere is cold and dry today, but
  • There was once liquid water flowing over the
  • surface.
  • Where did the water and early atmosphere go?
  • Where's the greenhouse atmosphere that allowed water to be liquid at the surface?
  • H2O and CO2 can go into the crust or be lost to space.
  • MAVEN will focus on the loss to space.

Ancient Valleys

Turn-off of the Martian magnetic field allowed turn-on of solar-extreme ultraviolet (EUV) and solar-wind stripping of the atmosphere approximately 3.7-4.1 billion years ago, resulting in the present thin, cold atmosphere.

other science content relevant to maven
Other science content relevant to MAVEN

Ionosphere: Ultraviolet (UV) and Extreme Ultraviolet (EUV) light from the Sun strips off electrons from the atoms and molecules in atmospheres (ionizes the atoms and molecules), leaving many ions and electrons. UV and EUV light also breaks apart molecules.

This mixture of the upper neutral atmosphere and ions and electrons is called the ionosphere.

Charged particles from the solar wind (mostly electrons and protons) also ionize Mars’ atmosphere.

Oxygen atoms, O + EUV-> Oxygen Ions, O+ + e-

CO2 atoms + EUV -> CO+ + O + e-

Carbon atoms, C + EUV -> C+ + e-

Helium atoms, He + EUV -> He++ + e-

… etc

Ionosphere

maven science questions
MAVEN Science Questions

What is the current state of the upper atmosphere?

What is the escape rate at the current epoch and how does it relate to the controlling processes?

What has the total loss to space been over time?

MAVEN will answer questions about the history of Martian volatiles and atmosphere and help us to understand the nature of planetary habitability.

the maven spacecraft
The MAVEN Spacecraft

LPW (2)

SWEA

SWIA

“Gull-Wing” Solar Arrays

SEP

Fixed HGA

MAG (2)

SEP

Articulated Payload Platform (IUVS/STATIC/NGIMS)

atoms
Atoms
  • What three subatomic particles make up atoms?
atoms1
Atoms
  • What three subatomic particles make up atoms?
  • The subatomic particles that make up atoms are protons, neutrons, and electrons.
atoms2
Atoms
  • Atoms are incredibly small. Placed side by side, 100 million atoms would make a row only about 1 centimeter long—about the width of your little finger!
  • The subatomic particles that make up atoms are protons, neutrons, and electrons.
  • The subatomic particles in a carbon atom are shown.
protons and neutrons
Protons and Neutrons
  • Protons and neutrons have about the same mass.
  • Protons are positively charged particles (+) and neutrons carry no charge at all.
  • Strong forces bind protons and neutrons together to form the nucleus,at the center of the atom.
electrons
Electrons
  • The electron is a negatively charged particle (–) with only 1/1840 the mass of a proton.
  • Electrons are in constant motion in the space surrounding the nucleus. They are attracted to the positively charged nucleus but remain outside the nucleus because of the energy of their motion.
electrons1
Electrons
  • Because atoms have equal numbers of electrons and protons, their positive and negative charges balance out, and atoms themselves are electrically neutral. The carbon atom shown has 6 protons and 6 electrons.

An atom that loses electrons becomes positively charged. An atom that gains electrons has a negative charge. These positively and negatively charged atoms are known as ions.

why the ion osphere

(+)

Why the Ionosphere?

(+)

UV light from the sun hits atoms in Earth’s upper atmosphere. The energy from this light knocks an electron off the atom, leaving a free electron and an Ion. This type of ionized gas is called a plasma. Unlike other gases, it can conduct an electric charge and is affected by magnetic fields.

solar wind interaction with a body with an atmosphere
Solar Wind Interaction with a Body with an Atmosphere
  • The sunlight partially ionizes the dayside atmosphere. Some of this flows to night side.
  • The solar wind is absorbed by the planetary atmosphere.
  • If the solar wind is magnetized, it cannot immediately enter the ionosphere, so the planet becomes an obstacle to the solar wind flow.
pressure balance between solar wind and ionosphere
Pressure Balance between Solar Wind and Ionosphere
  • The solar wind exerts dynamic pressure (ρu2) plus some magnetic and thermal pressure.
  • The ionosphere exerts thermal pressure force against the solar wind at the ionopause.
  • The pressure at the peak of the ionosphere is generally greater than that of the solar wind.
  • If the standoff distance is well above the collisional region, then the magnetic field will not diffuse into the ionosphere.
slide29

The remaining slides illustrate some of the technical details related to the Sun’s magnetic field, how it picks up and carries an ion away from Mars, and how the same basic process can cause “sputtering”.

The underlying physical concepts are typically taught in college-level courses…

slide30

Mars orbit

Slow solar wind IMF

Fast solar wind IMF

Sun

Mars

The interplanetary magnetic field (IMF) from the Sun moves similar to the animations shown on this webpage:

http://www.swpc.noaa.gov/wmo/solar-wind.php …Mars’s orbit would be close to the edge of the images

slide31

Looking down on Mars, Sun to the left, IMF lines in the plane parallel to page and above Mars’s “north pole” (north pole is designated by the star)

Slow solar wind IMF moving left to right

Mars orbit

slide32

Looking at Mars from the side, sun to the left, Mars orbit going into page. IMF moving left to right.

Slow solar wind IMF (lines coming out of page [mostly]) moving left to right

slide33

Ion Pickup

Looking at Mars from the side, sun to the left, Mars orbit going into page. IMF moving left to right.

Ion suddenly created, becomes swept up by the IMF (ion starts orbiting/gyrating around the field lines and get carried away by the moving IMF)

A charged particle that is moving relative to a magnetic field (or vice versa) moves like 0:36-0:53 in this video: http://www.youtube.com/watch?v=slmV2IlluAM

Slow solar wind IMF (lines coming out of page [mostly]) moving left to right

slide34

Ion Pickup

Looking at Mars from the side, sun to the left, Mars orbit going into page. IMF moving left to right.

As the ion spins around a magnetic field (which is moving very quickly from left to right), the ion’s path traces out a cycloid: http://archives.math.utk.edu/visual.calculus/0/parametric.5/

Zoomed out…

Slow solar wind IMF (lines coming out of page [mostly]) moving left to right

slide35

Ion Pickup

Looking at the day side of Mars, Sun is directly behind you, Mars orbit is right to left.

Same ion spins around the IMF line, gets carried in the direction into the page… does NOT move left or right.

View from the Sun…

Slow solar wind IMF (moving in the direction into page [mostly])

slide36

Looking at Mars from the side, sun to the left, Mars orbit going into page. IMF moving left to right.

Sputtering

(from a pickup ion)

Ion suddenly created, becomes swept up by the quickly moving IMF, then accelerates and slams into atmosphere, causing a chain reaction that sends other particles flying away (similar to billiard balls).

Slow solar wind IMF (lines coming out of page [mostly]) moving left to right