July 17, 2007 NMSU Campus

SomePLANETARY SCIENCE

Topics

Jim MurphyDepartment of Astronomy

New Mexico State UniversityLas Cruces, NM

July 17, 2007 NMSU Campus

A ‘soon to launch’Mars Spacecraft Mission

The Mars Phoenix Lander(1st launch opportunity: Aug 3rd)

(Mars arrival & landing: May 25th, 2008)

July 17, 2007 NMSU Campus

The scientific motivation for the Phoenix Lander

isto investigate the probable presence

of near-surface water ice at highnorthen martian latitudes

North Pole South Pole(to 60 degrees N) (to 60 degrees S)

July 17, 2007 NMSU Campus

The Mars Phoenix Landeris a STATIC lander (not a rover)

July 17, 2007 NMSU Campus

The Mars Phoenix Lander will ‘excavate’ the near-surface ‘soil’ and analyze its contents for ice and other materials….

July 17, 2007 NMSU Campus

Let’s Make a Planet…

The Fun New Game ShowThe Fun New Game Show Sweeping the Solar SystemSweeping the Solar System

July 17, 2007 NMSU Campus

WHAT IS OUR SOLAR SYSTEM?

The collection of:- our star (the Sun)

- the nine 8 planets that orbit this star (some big, some

small)- asteroids and comets (that also orbit around the star)- moons that themselves orbit around the planets (and

asteroids!)- ring particles (orbiting the planets)- dust (which can become meteors)- 'Kuiper Belt' objects (Pluto ??? … and beyond)

HOW DID ALL OF THESE OBJECTS COME TO BE ASSOCIATED AS THEY ARE?

July 17, 2007 NMSU Campus

Our Solar System as we know it

The SunRocky, metal planets

and moons

Gas Giant Planets

Asteroids(in the Asteroid Belt)

Comets

Almost all of these objects orbit the Sun in the same direction

within the same flat plane (like a spinning DVD)

July 17, 2007 NMSU Campus

Let’s try to determine how planets were formed….

Let’s Make a Planet

You, the contestant, can choose from amongst…

Door #1‘Capture by the Sun’

Door #2‘The Spitting Sun’

Door #3‘Dust Clumping’

July 17, 2007 NMSU Campus

DOOR #1: ‘Capture’ Let’s imagine that some magical process is responsible for forming stars and planets, and asteroids and comets, each independently (each forms on its own very far apart from one another) throughout the Galaxy

WHAT WOULD BE THE RESULTANT STRUCTURE OF THE SOLAR SYSTEM?

Solar System CAPTURE THEORY of formationIDEA: The Sun has “captured” (via gravity) all of the objects now orbiting around it

What is wrong with this idea?

Door #1‘Capture by the Sun’

July 17, 2007 NMSU Campus

A ‘CAPTURED’ Solar System

The SunRocky, metal planets

and moons

Gas Giant Planets

Asteroids(in the Asteroid Belt)

Comets

If the objects in the Solar System were “CAPTURED” by the

Sun, they would be moving in random directions around the Sun

July 17, 2007 NMSU Campus

So,So,A CAPTURE scenario A CAPTURE scenario

would produce a Solar System would produce a Solar System that that

DOES NOT look DOES NOT look like our Solar Systemlike our Solar System

..and we still would not have any idea how planets actually form....and we still would not have any idea how planets actually form..and why some are GAS GIANT and some are TERRESTRIALand why some are GAS GIANT and some are TERRESTRIAL

July 17, 2007 NMSU Campus

DOOR #2: ‘The Spitting Sun’ Let’s imagine that the Sun ‘spits out’ some of its ownmaterial, and that this ‘spat out’ material collects together to form a planet orbiting the Sun

WHAT WOULD BE THE RESULTANT STRUCTURE OF THE SOLAR SYSTEM ?

Solar System FISSION THEORY of formationIDEA: The Sun ‘burps’ out material to form planets

What is wrong with this idea?

Door #2‘The Spitting Sun’

July 17, 2007 NMSU Campus

The “Burping” Sun

These ‘spat out’ planets would have compositionsidentical to the Sun’s composition, which is dominatedby the gases hydrogen and helium…..Earth is composedof rock and metal,..the gas Giants do have hydrogen and helium, but not as much (relatively) as the Sun

July 17, 2007 NMSU Campus

So,So,A SPITTING SUN scenario A SPITTING SUN scenario

would produce a Solar System would produce a Solar System that that

DOES NOT look DOES NOT look like our Solar Systemlike our Solar System

..and we do not know of a physical mechanism by which the..and we do not know of a physical mechanism by which theSun can ‘burp out’ so much mass at one time……Sun can ‘burp out’ so much mass at one time……

July 17, 2007 NMSU Campus

DOOR #3: ‘Dust Clumping’ Let’s imagine that a really, really big (and massive)cloud of gas (and some dust) within the Galaxycollapses under its own gravitational pull upon itself

WHAT WOULD BE THE RESULTANT STRUCTURE OF THE SOLAR SYSTEM ?

Solar System CLOUD COLLAPSE of formationIDEA: A cloud of gas (and some dust) collapses,forms a rotating disk of gas and dust, has a star “turn on” at its center, and dust within the disk material clumps and gravitationally sticks together to form objects which might grow to be planets

Door #3‘Dust Clumping

July 17, 2007 NMSU Campus

Collapsing Gas Cloud..as seen from the side

At the center of the cloud, the collection of gas becomes verydense, and nuclear fusion sets in…A STAR IS BORN ! Dust within the disk, which is rotating around the new star, beginsto lump together forming large objects (some destined to becomePlanets)… far from the Sun, these ‘clumps’ can also grab cold gas

July 17, 2007 NMSU Campus

Collapsing Rotating Gas Cloud..as seen from above

At the center of the cloud, the collection of gas becomes verydense, and nuclear fusion sets in…A STAR IS BORN ! Dust within the disk, which is rotating around the new star, beginsto lump together forming large objects (some destined to becomePlanets)… far from the Sun, these ‘clumps’ can also grab cold gas

Gas Giant Planets

Rock-metal Planets

July 17, 2007 NMSU Campus

So,So,A CLUMPING scenario A CLUMPING scenario

can produce a Solar System can produce a Solar System that that

DOES look DOES look like our Solar Systemlike our Solar System

..and accounts for rock-metal planets near to the Sun and..and accounts for rock-metal planets near to the Sun andGas Giants far from the Sun based upon temperature……Gas Giants far from the Sun based upon temperature……

July 17, 2007 NMSU Campus

significant gas DOES NOT accumulate around the planet……significant gas DOES NOT accumulate around the planet……

Near to the young Sun, within the disk, gas molecules werefast because the gas there was HOT….. The gravitationalpull of these growing planets was not strong enough to graband hold these fast-moving gas (hydrogen and helium) molecules and atoms

July 17, 2007 NMSU Campus

so significant gas DOES accumulate around the planet……so significant gas DOES accumulate around the planet……

Far from the young Sun, within the disk, gas molecules wereslow because the gas there was COLD….. The gravitationalpull of these growing planets WAS strong enough to graband hold these slow-moving gas (hydrogen and helium) molecules and atoms

July 17, 2007 NMSU Campus

So,So,A CLUMPING scenario A CLUMPING scenario

can produce a Solar System can produce a Solar System that that

DOES look DOES look like our Solar Systemlike our Solar System

..and accounts for rock-metal planets near to the Sun and..and accounts for rock-metal planets near to the Sun andGas Giants far from the Sun based upon temperature……Gas Giants far from the Sun based upon temperature……

July 17, 2007 NMSU Campus

Are there any observationsAre there any observationswhich support this idea ofwhich support this idea of

CLUMPING……?CLUMPING……?the so-calledthe so-called

SOLAR NEBULASOLAR NEBULAHypothesisHypothesis

..why yes, indeed, such observations do exist !!..why yes, indeed, such observations do exist !!

July 17, 2007 NMSU Campus

HUBBLE SPACE HUBBLE SPACE TelescopeTelescope

images do show the presenceimages do show the presenceof gas and dust cloudsof gas and dust clouds

surrounding young starssurrounding young stars

July 17, 2007 NMSU Campus

DISK (seen edge-on)

STAR (at the center)

July 17, 2007 NMSU Campus

DISK (seen edge-on)

STAR (at the center)

Star’s light is ‘blocked out’

Planet forming within the dust disk?

July 17, 2007 NMSU Campus

A Hubble Space Telescope image of theOrion Nebula, a region in our Galaxy inwhich many stars are being ‘born’

July 17, 2007 NMSU Campus

A ‘protoplanetary’ disk seen ‘flat on’; thisstar and its associated disk are located within the Orion Nebula

July 17, 2007 NMSU Campus

So, current thought is:So, current thought is:

Planets form from materialPlanets form from materialwithin a collapsing gas cloud.within a collapsing gas cloud.The rotating disk results in allThe rotating disk results in allof the planets orbiting withinof the planets orbiting within

the same direction the same direction and in same plane.and in same plane.

Observations support this idea.Observations support this idea.

July 17, 2007 NMSU Campus

DOOR #3DOOR #3““CLUMPING”CLUMPING”

is the winner !!!is the winner !!!

Thanks for playing..Thanks for playing..

Let’s Make a Planet…

DOOR #3DOOR #3““CLUMPING”CLUMPING”

..one final item

July 17, 2007 NMSU Campus

..one final item Just as New Mexico experiences dust devils…….

A dust devil

So too does Mars !

July 17, 2007 NMSU Campus

Dust devils ‘dancing’ across Mars’ surfaceas observed by the Mars SPIRIT Rover

Gusev Crater, Mars

July 17, 2007 NMSU Campus

Let’s build some planets !!

Jim Murphy

Department of AstronomyNew Mexico State University

Las Cruces, NM

July 17, 2007 NMSU Campus

ASTR 508Astronomy for Educators

Fall 2007: online offering

Dr. Bernie McNamaraNMSU’s masters of Art

in Teaching Degree Program