July 17, 2007NMSU Campus Some PLANETARY SCIENCE Topics Jim Murphy Department of Astronomy New Mexico State University Las Cruces, NM

July 17, 2007NMSU Campus A ‘soon to launch’ Mars Spacecraft Mission The Mars Phoenix Lander (1 st launch opportunity: Aug 3 rd ) (Mars arrival & landing: May 25 th, 2008)

July 17, 2007NMSU Campus The scientific motivation for the Phoenix Lander is to investigate the probable presence of near-surface water ice at high northen martian latitudes North Pole South Pole (to 60 degrees N) (to 60 degrees S)

July 17, 2007NMSU Campus The Mars Phoenix Lander is a STATIC lander (not a rover)

July 17, 2007NMSU Campus The Mars Phoenix Lander will ‘excavate’ the near-surface ‘soil’ and analyze its contents for ice and other materials….

July 17, 2007NMSU Campus Let’s Make a Planet… The Fun New Game Show Sweeping the Solar System Sweeping the Solar System

July 17, 2007NMSU 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, 2007NMSU Campus Our Solar System as we know it The Sun Rocky, 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, 2007NMSU 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, 2007NMSU 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 formation IDEA: 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, 2007NMSU Campus A ‘CAPTURED’ Solar System The Sun Rocky, 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, 2007NMSU CampusSo, A CAPTURE scenario would produce a Solar System that DOES NOT look like our Solar System..and we still would not have any idea how planets actually form.. and why some are GAS GIANT and some are TERRESTRIAL

July 17, 2007NMSU Campus DOOR #2: ‘The Spitting Sun’ Let’s imagine that the Sun ‘spits out’ some of its own material, 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 formation IDEA: The Sun ‘burps’ out material to form planets What is wrong with this idea? Door #2 ‘The Spitting Sun’

July 17, 2007NMSU Campus The “Burping” Sun These ‘spat out’ planets would have compositions identical to the Sun’s composition, which is dominated by the gases hydrogen and helium…..Earth is composed of rock and metal,..the gas Giants do have hydrogen and helium, but not as much (relatively) as the Sun

July 17, 2007NMSU CampusSo, A SPITTING SUN scenario would produce a Solar System that DOES NOT look like our Solar System..and we do not know of a physical mechanism by which the Sun can ‘burp out’ so much mass at one time……

July 17, 2007NMSU Campus DOOR #3: ‘Dust Clumping’ Let’s imagine that a really, really big (and massive) cloud of gas (and some dust) within the Galaxy collapses under its own gravitational pull upon itself WHAT WOULD BE THE RESULTANT STRUCTURE OF THE SOLAR SYSTEM ? Solar System CLOUD COLLAPSE of formation IDEA: 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, 2007NMSU Campus Collapsing Gas Cloud..as seen from the side At the center of the cloud, the collection of gas becomes very dense, and nuclear fusion sets in…A STAR IS BORN ! Dust within the disk, which is rotating around the new star, begins to lump together forming large objects (some destined to become Planets)… far from the Sun, these ‘clumps’ can also grab cold gas

July 17, 2007NMSU Campus Collapsing Rotating Gas Cloud..as seen from above At the center of the cloud, the collection of gas becomes very dense, and nuclear fusion sets in…A STAR IS BORN ! Dust within the disk, which is rotating around the new star, begins to lump together forming large objects (some destined to become Planets)… far from the Sun, these ‘clumps’ can also grab cold gas Gas Giant Planets Rock-metal Planets

July 17, 2007NMSU CampusSo, A CLUMPING scenario can produce a Solar System that DOES look like our Solar System..and accounts for rock-metal planets near to the Sun and Gas Giants far from the Sun based upon temperature……

July 17, 2007NMSU 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 were fast because the gas there was HOT….. The gravitational pull of these growing planets was not strong enough to grab and hold these fast-moving gas (hydrogen and helium) molecules and atoms

July 17, 2007NMSU 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 were slow because the gas there was COLD….. The gravitational pull of these growing planets WAS strong enough to grab and hold these slow-moving gas (hydrogen and helium) molecules and atoms

July 17, 2007NMSU CampusSo, A CLUMPING scenario can produce a Solar System that DOES look like our Solar System..and accounts for rock-metal planets near to the Sun and Gas Giants far from the Sun based upon temperature……

July 17, 2007NMSU Campus Are there any observations which support this idea of CLUMPING……? the so-called SOLAR NEBULA Hypothesis..why yes, indeed, such observations do exist !!

July 17, 2007NMSU Campus HUBBLE SPACE Telescope images do show the presence of gas and dust clouds surrounding young stars

July 17, 2007NMSU Campus DISK (seen edge-on) STAR (at the center)

July 17, 2007NMSU Campus DISK (seen edge-on) STAR (at the center) Star’s light is ‘blocked out’ Planet forming within the dust disk?

July 17, 2007NMSU Campus A Hubble Space Telescope image of the Orion Nebula, a region in our Galaxy in which many stars are being ‘born’

July 17, 2007NMSU Campus A ‘protoplanetary’ disk seen ‘flat on’; this star and its associated disk are located within the Orion Nebula

July 17, 2007NMSU Campus So, current thought is: Planets form from material within a collapsing gas cloud. The rotating disk results in all of the planets orbiting within the same direction and in same plane. Observations support this idea.

July 17, 2007NMSU Campus DOOR #3 “CLUMPING” is the winner !!! Thanks for playing.. Let’s Make a Planet… DOOR #3 “CLUMPING”..one final item

July 17, 2007NMSU Campus..one final item Just as New Mexico experiences dust devils……. A dust devil So too does Mars !

July 17, 2007NMSU Campus Dust devils ‘dancing’ across Mars’ surface as observed by the Mars SPIRIT Rover Gusev Crater, Mars

July 17, 2007NMSU Campus Let’s build some planets !! Jim Murphy Department of Astronomy New Mexico State University Las Cruces, NM

July 17, 2007NMSU Campus ASTR 508 Astronomy for Educators Fall 2007: online offering Dr. Bernie McNamara NMSU’s masters of Art in Teaching Degree Program