New Worlds, Living Large

Out of the Dust, A Planet is Born
Image Credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)

Six years ago, then NASA Associate Administrator Wesley Huntress, Jr., stated , "Wherever liquid water and chemical energy are found, there is life. There is no exception." Few opportune years like 2004 have presented astrobiology with as many remarkable vistas and fresh perspectives on this fundamental triad of water, chemical energy and life.

Consider this year’s accomplishments of those dedicated to searching for life in the universe.

Landing on Mars not once, but twice. Then finding evidence for water on opposite sides of the red planet. Picking up what appears to be methane signals in the martian atmosphere, one of the residues that might prove one day to be the product of underground biology. Scientists began to discuss seriously what colonization strategies make sense.

Setting off to explore the even richer atmosphere of the Earth-like moon, Titan. Spiraling into orbital capture around Saturn and photographing its majestic rings.

Flying through the tail of a comet and heading home after collecting the first extraterrestrial samples from such dusty iceballs. Launching the Deep Impact probe to smash into a comet and watch how the dust and ice get kicked up.

Scene from a moon orbiting the extra-solar planet in orbit around the star HD70642.
Credit:David A. Hardy, (c)

Filling the astronomy catalogs with well over a hundred new planets, including what may prove to be the first visible exoplanet. Finding some nearby candidates that might occupy temperate locations or safely orbit Sun-like stars.

Witnessing the once-per-century passage of our neighboring Venus across the face of the Sun. The MESSENGER probe took off on its decade long tour of the inner solar system to orbit Mercury.

Discovering the largest planetoids beyond Pluto among those outer nurseries where only comets visit.

The editors of Astrobiology Magazine revisit the highlights of the year and where possible point to one of the strongest lineups ever for beginning a new turn of the calendar. Between the marathon still being run by the twin Mars rovers and the expected descent to Saturn’s moon, Titan, next year promises no letdowns.

Number three on the countdown of 2004 highlights was the remarkable progress made in discovering new worlds orbiting other stars. Planet hunting began in earnest only about 10 years ago, but today spans numerous catalogs detailing orbits, diameters and temperatures.

Artist concept of star system, HD70642.
Credit:John Rowe animation

Discovering new planets is the culmination of a decade’s work in theoretical and observational astronomy. While last year witnessed the first 100 prospective planets identified, this year brought significant outliers into the equation. Most of the planets discovered so far have been large, hot worlds–sometimes called ‘hot Jupiters’. These planets offer little prospects for habitability. The motions of these closer-in giants prevent terrestrial planets from forming stable orbits in the habitable zone. But a solar system with a large planet in a circular orbit five times larger than our own orbit- even a Neptune-sized planet – is a solar system in which a habitable Earth-like planet could exist quite comfortably.

2004 signalled the introduction of younger planets than ever thought possible to view as well as tantalizing hints of how to visualize such a pale blue dot when found.

In June, University of Rochester researchers suggested the possibility of a planet on the order of only 100,000 to half a million years old, a finding that defied expectations that young stars might form planets from a dusty disk in such a short period.

Astronomers also passed a milestone of cataloguing properties for more than 130 planets orbiting nearby stars in our galaxy. Although the solar systems they have found are very different from ours, by studying the planets that have been found – their masses, their orbits and their stars – they are uncovering intriguing hints that our galaxy may be brimming with solar systems like our own. How many of the known exoplanetary systems might contain habitable Earth-type planets? Perhaps half of them, reported a team from the Open University, led by Professor Barrie Jones, in April. Popularly known as the "Goldilocks" zone, this region would be neither too hot for liquid water, nor too cold.

What Next?

– Mars Reconnaissance Orbiter (MRO) launch, Mars Orbiter to collect high-resolution, 1-meter, images in stereo-view of Mars
– European Venus Express, Venus Orbiter for two-year nominal mapping life [486 days, two Venus year]

New Horizons, Pluto and moon Charon flyby, mapping to outer solar system cometary fields and Kuiper Belt
Dawn, Asteroid Ceres and Vesta rendezvous and orbiter, including investigations of asteroid water and influence on meteors
Kepler, Extrasolar Terrestrial Planet Detection Mission, designed to look for transiting or earth-size planets that eclipse their parent stars [survey 100,000 stars]
Europa Orbiter, planned Orbiter of Jupiters ice-covered moon, Europa, uses a radar sounder to bounce radio waves through the ice
– Japanese SELENE Lunar Orbiter and Lander, to probe the origin and evolution of the moon

– Japanese Planet-C Venus Orbiter, to study the Venusian atmosphere, lightning, and volcanoes.
– Mars Scout mission, final selections August 2003 from four Scouts: SCIM, ARES, MARVEL and Phoenix
– French Mars Remote Sensing Orbiter and four small Netlanders, linked by Italian communications orbiter

BepiColumbo, European Mercury Orbiters and Lander, including Japanese collaborators, lander to operate for one week on surface
Mars 2009, proposed long-range rover to demonstrate hazard avoidance and accurate landing dynamics

Related Web Pages

2003: Year in Review
Solar System Exploration Survey
Mars Opportunity Rover
Mars Spirit Rover
Mars Express
Mars Methane
New Planets
Saturn Cassini
Venus Occultation
Planet Ten: Beyond Pluto?