Robots In Space

Some of this actually made the lamestream media, so there may actually be a tiny fraction of the population already aware of the great science returned this week by our fleet of robotic explorers.

Their successes serve to underscore the idiocy of ramping up a manned space program with no tangible objectives by gutting the budget for future robotic missions. Given a choice between idiocy and rationality in managing this nation’s expenditures on space science, of course our politicians — led, I’m sorry to report, by George W. Bush — are choosing idiocy.

Sigh.

The big news of the week was from the Cassini mission, where NASA announced the discovery of liquid water on Enceladus, one of the strange moons of Saturn. The graphic at right is from NASA, and shows one possible mechanism the explains the (very much) unexpected presence of liquid water in the cold environs of Saturn.

From NASA’s press release:

As Saturn’s active moon Enceladus continues to spew icy particles into space, scientists struggle to understand the mechanics of what is going on beneath the fractured south polar terrain. This graphic illustrates key aspects of the model proposed by the Cassini imaging science team in a paper published in the journal Science on March 10, 2006.

The model shows how proposed underground reservoirs of pressurized liquid water above 273 degrees Kelvin (0 degrees Celsius) could fuel geysers that send jets of icy material into the skies above the moon’s south pole. In the graphic, the vent to the surface pierces one of the “tiger stripe” fractures seen in Cassini views of the southern polar terrain (see Tiger Stripes Up Close for a look at the tiger stripes). Temperatures increase with depth.

Some combination of internal radioactive decay and flexing — perhaps concentrated within the tiger stripe fractures and brought about by the particular characteristics of Enceladus' orbit — is implicated as the source of the heat creating the liquid reservoirs. However, it is not yet clear how the deep interior of Enceladus functions, nor whether the moon is fully differentiated (separated into layers, with rock at the center and ice outside).

The main significance of liquid water is of course that its presence is one of the key precursors for life-as-we-know-it (LAWKI), meaning life based on carbon chemistry, with a major dependence on water as the matrix in which much of that chemsitry occurs. On earth, under the conditions hypothesized by the NASA scientists to explain liquid water on Enceladus, there would be life. This certainly doesn’t “prove” that Enceladus harbors LAWKI lifeforms — but it sure makes folks much more curious to find out if that’s the case.

Something you probably won’t hear from the lamestream media: this finding on Enceladus is a splendid example of why robots make better space explorers than humans. Cassini will spend several years studying Saturn and it’s moons; a manned mission could spend weeks at best. Cassini is free to spend months in space as it wanders from one moon to another; a manned mission couldn’t realistically do that. And Cassini can visit repeatedly (it will be back to Enceladus in 2008), whereas a manned mission would be little more than a one night stand. These capabilities overwhelm the cognitive and observational superiorities of humans — and the better our technology for instrumentation gets, the greater that gap becomes.

In other space news, the Mars Reconnaissance Orbiter (MRO) successfully inserted itself into orbit around Mars.

From the NASA press release:

The spacecraft, Mars Reconnaissance Orbiter, will provide more science data than all previous Mars missions combined.

Signals received from the spacecraft at 2:16 p.m. Pacific Time after it emerged from its first pass behind Mars set off cheers and applause in control rooms at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and at Lockheed Martin Space Systems, Denver.

"This is a great milestone to have accomplished, but it’s just one of many milestones before we can open the champagne,” said Colleen Hartman, deputy associate administrator for NASA’s Science Mission Directorate. “Once we are in the prime science orbit, the spacecraft will perform observations of the atmosphere, surface, and subsurface of Mars in unprecedented detail."

The spacecraft traveled about 500 million kilometers (310 million miles) to reach Mars after its launch from Florida on Aug. 12, 2005. It needed to use its main thrusters as it neared the planet in order to slow itself enough for Mars' gravity to capture it. The thruster firing began while the spacecraft was still in radio contact with Earth, but needed to end during a tense half hour of radio silence while the spacecraft flew behind Mars.

"Our spacecraft has finally become an orbiter,” said JPL’s Jim Graf, project manager for the mission. “The celebration feels great, but it will be very brief because before we start our main science phase, we still have six months of challenging work to adjust the orbit to the right size and shape."

For the next half-year, the mission will use hundreds of carefully calculated dips into Mars' atmosphere in a process called “aerobraking.” This will shrink its orbit from the elongated ellipse it is now flying, to a nearly circular two-hour orbit. For the mission’s principal science phase, scheduled to begin in November, the desired orbit is a nearly circular loop ranging from 320 kilometers (199 miles) to 255 kilometers (158 miles) in altitude, lower than any previous Mars orbiter. To go directly into such an orbit instead of using aerobraking, the mission would have needed to carry about 70 percent more fuel when it launched.

The instruments on Mars Reconnaissance Orbiter will examine the planet from this low-altitude orbit. A spectrometer will map water-related minerals in patches as small as a baseball infield. A radar instrument will probe for underground layers of rock and water. One telescopic camera will resolve features as small as a card table. Another will put the highest-resolution images into broader context. A color camera will monitor the entire planet daily for changes in weather. A radiometer will check each layer of the atmosphere for variations in temperature, water vapor and dust.

"The missions currently at Mars have each advanced what we know about the presence and history of water on Mars, and one of the main goals for Mars Reconnaissance Orbiter is to decipher when water was on the surface and where it is now,” said JPL’s Dr. Richard Zurek, project scientist for the mission. “Water is essential for life, so that will help focus future studies of whether Mars has ever supported life."

The orbiter can radio data to Earth at up to 10 times the rate of any previous Mars mission. Besides sending home the pictures and other information from its own investigations, it will relay data from surface missions, including NASA’s Phoenix Mars Scout scheduled for launch in 2007 and Mars Science Laboratory in development for 2009.

Scientists studying Mars have been waiting for MRO with great anticipation — I think almost in equal measure for the instruments MRO carries (and will use in long-term observations) and for the added communications capabilities MRO brings to the Mars neighborhood. MRO is partly an “upgrade” to current robots already at Mars, and even to robots yet to arrive. A poor analogy: its a bit like what happens to a town when they first get a telephone system installed.

And last, but certainly not least, the plucky Martian Rovers (Spirit and Opportunity) are still rambling around on the surface of Mars, doing great science work every day.

From the NASA Press Release:

The panoramic camera aboard NASA’s Mars Exploration Rover Opportunity acquired this panorama of the “Payson” outcrop on the western edge of “Erebus” Crater during Opportunity’s sol 744 (Feb. 26, 2006). From this vicinity at the northern end of the outcrop, layered rocks are observed in the crater wall, which is about 1 meters (3.3 feet) thick. The view also shows rocks disrupted by the crater-forming impact event and subjected to erosion over time.

To the left of the outcrop, a flat, thin layer of spherule-rich soils overlies more outcrop materials. The rover is currently traveling down this “road” and observing the approximately 25-meter (82-foot) length of the outcrop prior to departing Erebus crater.

The panorama camera took 28 separate exposures of this scene, using four different filters. The resulting panorama covers about 90 degrees of terrain around the rover. This approximately true-color rendering was made using the camera’s 753-nanometer, 535-nanometer and 423-nanometer filters. Image-to-image seams have been eliminated from the sky portion of the mosaic to better simulate the vista a person standing on Mars would see.

It would be hard to overstate the contributions these two little machines have made to our understanding of Mars. As in most scientific investigations, their discoveries have raised a lot more questions than they answered — but they sure have answered a lot! Thanks to them, we now know for sure something we’ve long suspected: the Martian surface once had standing and flowing water. For over two years now (long past the 90 day design lifetime), the rovers have been patiently exploring, returning panoramic photos like the one above, microscopic photos of rocks and minerals, detailed spectrographs at both long and short range, and much more. Amazing gadgets, they are…