Solar System NASA

8/12/2019 Solar System NASA

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Inner Solar System

Planetary Science missions, past, current, in planning or in development, extend mankinds presence

to the solar systems inner rocky worlds, helping to unlock the secrets of the solar systems

composition, history and evolution, and how life established itself on Earth.

Mercury is the least explored terrestrial or rocky planet in our solar system. Previously NASAsonly encounters with the innermost planet were the three flybys performed in 1974 and 1975 by the

Mariner 10 mission that mapped 45 percent of the planets surface. In January 2008, the

MESSENGER spacecraft flew by Mercury for its first of three fly-bys. As it begins to reveal the

planets composition and history, it will in turn, help scientists understand more about our home

planet and its place in the inner solar system.

Venus has often been described as Earths sister planet since the two are very similar in size and

bulk composition, although they evolved to very different ends. Venus is not currently targeted by

any NASA missions although future mission concepts include the Venus In Situ Explorer (VISE)

and Venus Mobile Explorer (VME) that would investigate the surface of Venus and help understand

the climate change processes that led to the extreme conditions of Venus today. A Venus SurfaceSample Return (VSSR) mission is also being considered. These missions remain long-range goals

for Venus exploration.

Earths Moon has a special place among the objects of the solar system, as it is the only body other

than Earth where humans have journeyed to and where humans will return relatively soon. NASA is

sending robotic missions to the moon to prepare for mans prolonged habitation on the lunar surface

which ultimately will help man reach for Mars and attain the goals set forth in the Vision for Space

Exploration (VSE). Studying the Moon and its history provides insight on the formation history of

the Earth-Moon system and events that shaped the inner solar system.

Mars is a highly attractive object of study: not only does it provide an excellent laboratory for

studying planetary evolution in the context of the Earth and Venus, but it is the most compellingtarget in the solar system to search for lifes existence beyond Earth. Additionally, Mars is an

eventual goal of the Vision for Space Explorations human spaceflight program. Finally, Mars is

relatively easily accessed with launch opportunities occurring approximately every 2 years. For

these reasons, the Mars Exploration Program is a fully integrated program, designed to maximize

the scientific return, technology infusion, and public engagement of the robotic exploration of the

Red Planet. Each strategic mission of the program has both technological and scientific linkages to

previous missions and orbiters, and landers support each others operations.

Outer Solar System

NASAs Planetary Science missions to the outer planets help reveal secrets about the solar system

by observing those outer distant worlds up close. Jupiters moon Europa and Saturns moon

Enceladus are now thought to hide liquid water beneath their frozen surfaces and are high priority

targets for NASA. Unlocking their secrets and those of the outer planets will help scientists

understand more about planet Earth and the formation and evolution of the solar system.

Jupiter has more mass than all other planets in the solar system combined. It helps protect Earth by

steering comets either towards the sun or ejecting them to the outer reaches of the solar system or

beyond. Jupiter has dozens of moons orbiting it, one of which, Europa, is thought to have a sub-

surface liquid salt water ocean. It therefore may possibly harbor life as heat and water, the two

ingredients required for life on Earth as we know it, are seemingly present below the moons

surface.


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Saturn has intrigued man for centuries, especially since the invention of the telescope when the

Saturns grand rings were observed for the first time. Much like Jupiter, Saturn has many dozens of

moons, one of which, Enceladus, could provide a foot-hold for life to form. Observations by the

Cassini spacecraft revealed Enceladus to have tenuous geyser and therefore heated liquid must be

lurking below the surface. Water and energy are essential to all forms of life on Earth and these two

constituents are what scientists treasure most in the search for life beyond our planet.

Uranus - Over the 20062016 timeframe, there are no strategic missions planned to Uranus and onlyone spacecraft, the extremely productive Voyager II, has ever visited the distant planet. Ultimately,

deep-entry probes into Uranus will be necessary in order to understand its composition and compare

it to that of the other water giant, Neptune.

Neptune poses a number of important questions regarding how giant planets form and what

truncates the formation of multiple giant planets in a planetary system. Residing on the edge of our

planetary system, Neptune may hold, deep in its interior, chemical clues concerning the nature of

the rocky and icy debris that formed the giant planets. A comprehensive study of Neptune, and its

moon Triton, is considered a priority for the third decade by the Solar System Exploration roadmap

team.Pluto was redefined in 2006 by the International Astronomical Union (IAU) as a dwarf Planet.

Throughout the scientific community there is still much debate about this definition and many

organizations have yet to weigh in. Pluto shares a region of its orbit with a collection of similar icy

bodies called Kuiper Belt Objects (KBOs). The Kuiper Belt is believed to represent the best

available record of the original interstellar materials that formed the solar nebula. This region is also

the birthplace of the short-period comets. Plutos orbit also crosses inside that of Neptunes which

renders Pluto a member of the Trans-Neptunian Object (TNO) class. Plutos moon, Charon, was

discovered in 1978, but more recently in 2005, two moonlets, Nix and Hydra were revealed in

telescopic surveys. The Pluto System is unique and the New Horizons mission will be the first

spacecraft to glimpse these distant icy bodies when it encounters the system in 2015.

Small Bodies of the Solar System

The small bodies in the solar system include comets, asteroids, the objects in the Kuiper Belt and

the Oort cloud, small planetary satellites, Triton, Pluto, Charon, and interplanetary dust. As some of

these objects are believed to be minimally altered from their state in the young solar nebula from

which the planets formed, they may provide insight into planet Earth and the formation and

evolution of the solar system.

The Oort Cloud is a spherical shell of millions of icy bodies which surrounds the solar system at

vast distances and is thought to be the birth place of long-period comets.

The Kuiper Belt is a region extending from Neptunes orbit out to the far and distant reaches of the

solar system and possibly holds the best available record of the original interstellar materials that

formed the solar nebula. This region beyond Neptune is also the most probable birthplace of the

short-period comets.

Comets are pristine remnants from the formation of the solar system that are comprised of minerals,

rock and mostly ice, much like a dirty snowball. They travel around the sun in elliptical orbits and

can be inclined to the plane of the solar system at any angle. Comets can sprout tails extending

many tens of millions of miles, during their closest approach to the sun. Short period comets are

thought to come from the Kuiper Belt on the outskirts of Neptunes orbit and further, and longer

period comets are thought to come from the Oort cloud, a vast spherical shell that surrounds the

solar system at a huge distance. Recent spacecraft encounters with comets seem to raise more

questions then they answer and some finds are quite unexpected. NASA targets some of thesebodies with spacecraft loaded with instrumentation that help tease out the secrets lurking in these

icy bodies.


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Pluto resides in the Kuiper Belt. With an orbit inclined to the plane of the solar system, Pluto most

likely evolved away from the suns flattened disk where the larger bodies (or planets) formed.

Plutos orbit crosses inside that of Neptunes rendering Pluto also a member of the Trans-Neptunian

Object (TNO) class. The Pluto system is very exotic, having three moons including Charon

discovered in 1978, and Nix and Hydra discovered in 2005.

Asteroids are rocky remnants from the formation of the solar system. They are not spherical andhave differing compositions and histories. Most, although not all asteroids, reside in a region

between Mars and Jupiter where numerous other small rocky worlds orbit the sun. Some asteroids

belong to groups that came from larger parent bodies which were shattered in past collisions with

other asteroids. Some are in orbits that cross paths with that of Earths or other planets. Asteroids

that cross Earths orbit are called Potentially Hazardous Asteroids (PHA) and the more we observe

the heavens, the more of them we find, some of which are seen for the first time just after passing

close to Earth.

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