Space Weathering

By Maxwell Justice

What is it? • What is Space Weathering?

– It is like erosion on earth but in space

• What causes Space Weathering?– Collisions of galactic and solar

cosmic rays– Irradiation, implantaion, and

sputtering from solar wind particles

– The bombardment by all sizes of meteorites and micrometeorites

“Whatever gave you that idea?”• Much of the knowledge on space

weathering comes from the lunar samples returned from the Apollo program.

• What was found to help support the idea was in the regolith a crystal formation called Agglutinates was discovered which is created from impacts on the surface by high velocity micrometeorites. They turn a portion of the regolith to glass and contain inside the glass nanophase iron.

• Nanophase iron is formed from the vapor caused by the impacts and give agglutinates its black appearance.

Micrometeorite Bombardment• Micrometeorites

constantly bombard the lunar surface

• Many are smaller than the size of a pencil head

• They can have an impact velocity of 100,000 km/h and using the E=(m*v^2), they have enough energy to vaporize the lunar soil glassy coat or “agglutinates”

Background

• Q. What are solar winds?• A. Solar wind is an ejection of charged

particles from the Sun’s upper atmosphere or the Corona. The solar winds extent the very edge of the solar system to create what is known as the heliosphere. The winds are full of harmful particles that can affect biology and technology.

How to recognize Space Weathering

• The physical effects of space weather– Become darker because the

albedo (or the reflectivity of an object) is reduced caused by the cosmic and solar radiation

– Becomes redder ( the reflectance increases with increasing wavelength) caused by the micrometeor bombardment

– The depth of diagnostic absorption bands (the portion of the spectrum that an element absorbs) are reduced

The Differences in the Earth and Moon from the Effects of Solar Winds

Earth• The earth’s magnetic field

prevents the solar winds from reaching the planet’s surface and in that, allows an atmosphere that supports and develops life.

Moon• The moon has no

detectable magnetic field to deflect the harmful solar winds and allows the charged particles to collide and collect in the lunar surface. Solar winds also prevents a life supporting atmosphere from developing.

Apollo MissionsThe Astronauts discovered in their missions were– The deposits from the winds

are of potential resources for future mission to the moon such as the element Helium 3

– Lunar dust is positively charged so clings to everything and gets into equipment

– The dust that snuck into the Lander caused a irritation in the lungs of the astronauts Harrison Schmitt called it “lunar dust hay fever

Space weathering on Mercury• Mercury being the closet

planet to the sun is constantly bombarded with solar radiation and winds. The impact velocity of micrometeorites is also much higher then that of lunar impacts.

• The closeness to the sun and higher impacts velocity on Mercury make it more efficient in creating the melt and vapor that form agglutinates on the surface.

Space Weathering on Mercury

• One effect from space weathering is not found on Mercury like the Moon. It is the red-ing of the soil. Because of this it is speculated that there is no iron composition on surface.

Space Weathering on Asteroids

Ceres, Pallas, Vesta, and Juno• Asteroids have no atmosphere

and very little gravitational attraction but space weathering is thought to occur on these bodies as well.

• The asteroid belt’s distance from the Sun mean fewer particles from solar winds and radiation reach them so less red-ing is noticeable.

• The little gravity asteroids have mean fewer impacts from micrometeorites so fewer vapor and melt surface compositions that form agglutinates

How did they determine space weathering on asteroids then?

• The redden portion of the spectrum given off by the moon, mercury and meteorites did not match up to ones in the asteroid belt. The S-type asteroids in particular.– S-type asteroids are silicaceous

composition.• Asteroids that have come close to

the earth have been noticed to have the same spectrum matching other known weathered objects, suggesting an ongoing process that actually flip-flops the spectral characteristics of the asteroids back and forth depending on where they are.

Space Weathering on Asteroids• More data to suggest

space weathering is taking place on asteroids are the fly-bys of probes to asteroids.

• The spectral analysis of impacts on the surfaces, particularly the fresh ones show a red-ing of the surface on S-types, showing the effects of solar radiation on the iron.

Citation

• http://antwrp.gsfc.nasa.gov/apod/image/0309/aldrinswc_apollo11_big.jpg

• http://science.nasa.gov/headlines/y2008/10apr_moondustinthewind.htm

• http://science.nasa.gov/headlines/y2006/28dec_truefake.htm

• http://en.wikipedia.org/wiki/Space_weathering

• http://en.wikipedia.org/wiki/Solar_winds