Universe Today

Image credit: NASA/JPL

The mast-mounted cameras on board the Mars Exploration Rovers, Spirit and Opportunity, will provide the best view so far of the surface of the Red Planet. The cameras are the equivalent of 20/20 human vision – with a resolution of one pixel/millimeter at a range of three metres. Their cameras can pan up and down 90-degrees, and look completely around 360-degrees. The first rover, Spirit, will arrive on Mars on January 3, with Opportunity arriving on January 25.

The Cornell University-developed, mast-mounted panoramic camera, called the Pancam, on board the rovers Spirit and Opportunity will provide the clearest, most-detailed Martian landscapes ever seen.

The image resolution – equivalent to 20/20 vision for a person standing on the Martian surface – will be three times higher than that recorded by the cameras on the Mars Pathfinder mission in 1997 or the Viking Landers in the mid-1970s.

From 10 feet away, Pancam has a resolution of 1 millimeter per pixel. “It’s Mars like you’ve never seen it before,” says Steven Squyres, Cornell professor of astronomy and principal investigator for the suite of scientific instruments carried by the rovers.

Spirit is scheduled to land on Mars on Jan. 3 at 11:35 p.m. EST. Opportunity will touch down Jan. 25 at 12:05 a.m. EST.

The Jet Propulsion Laboratory (JPL) in Pasadena, a division of the California Institute of Technology, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Cornell, in Ithaca, N.Y., is managing the rovers’ science instruments.

Pancam’s mast can swing the camera 360 degrees across the horizon and 90 degrees up or down. Scientists will know a rover’s orientation each day on the Martian surface by using data gained as the camera searches for and finds the sun in the sky at a known time of day. Scientists will determine a rover’s location on the planet by triangulating the positions of features seen on the distant horizon in different directions.

Rover science team member James Bell, Cornell associate professor of astronomy and the lead scientist for Pancam, says that high resolution is important for conducting science on Mars. “We want to see fine details. Maybe there is layering in the rocks, or the rocks are formed from sediments instead of volcanoes. We need to see the rock grains, whether they are wind-formed or shaped by water,” he says.

Also, Pancam is important for determining a rover’s travel plans. Says Bell: “We need to see details of possible obstacles that may be way off in the distance.”

As each twin-lens CCD (charge-coupled device) camera takes pictures, the electronic images will be sent to the rover’s onboard computer for a number of image processing steps, including compression, before the data are sent to Earth.

Each image, reduced to nothing more than a stream of zeros and ones, will be part of a once- or twice-daily stream of information beamed to Earth, a journey that takes 10 minutes. The data will be retrieved by NASA’s Deep Space Network, delivered to mission controllers at JPL and converted into raw images. From there, the images will be sent to the new Mars image processing facility at Cornell’s Space Sciences Building, where researchers and students will hover over computers to produce scientifically useful pictures.

During the surface activity by the rovers, from January to May 2004, there will be daily extensive planning by the Mars scientific team, led by Squyres. Research specialists Elaina McCartney and Jon Proton will participate in these meetings and decide how to implement the plans for Pancam and each rover’s five other instruments.

Processing pictures from 100 million miles away will be no easy feat. It took three years for Cornell faculty, staff and students to precisely calibrate the Pancam lenses, filters and detectors, and to write the software that tells the special camera what to do.

For instance, researchers Jonathan Joseph and Jascha Sohl-Dickstein wrote and perfected software that will produce images of great clarity. One of Joseph’s software routines patches the images together into larger pictures, called mosaics, and another brings out details within single images. Sohl-Dickstein’s software will allow scientists to generate color pictures and conduct spectral analysis, which is important in understanding the planet’s geology and composition.

Extensive work on the camera also was accomplished by Cornell graduates Miles Johnson, Heather Arneson and Alex Hayes. Hayes, who started working on the Mars mission as a Cornell sophomore, built a mock-up of the panoramic camera that aided the delicate color calibration and calculation of the actual Mars camera’s focal length and field of view. Johnson and Arneson spent eight months at JPL running Pancam under Mars-like conditions and collecting calibration data for the camera’s 16 filters.

For the students and recent graduates on the Pancam team, the research has been both valuable experience and education. “I stood inside a clean room at the Jet Propulsion Laboratory and performed testing on the real rovers,” says Johnson. “It was a weird but an exciting feeling standing next to such a really complex piece of equipment that would soon be on Mars.”

Original Source: Cornell University

Image credit: NASA/JPL

Scientists are always looking for more ways to cram scientific instruments into spacecraft, and they’ve come up with an innovative idea for the Mars Exploration rovers: using the wheels to dig trenches to see what the environment on Mars is like a few centimetres beneath the surface. Researchers from Cornell University perfected a technique where the rover locks all but one of its six wheels, and then uses the final wheel to churn up the dirt – tests in the lab allowed them to get at material which was more than 10 cm deep.

After the twin Mars Exploration Rovers bounce onto the red planet and begin touring the Martian terrain in January, onboard spectrometers and cameras will gather data and images — and the rovers’ wheels will dig holes.

Working together, a Cornell University planetary geologist and a civil engineer have found a way to use the wheels to study the Martian soil by digging the dirt with a spinning wheel. “It’s nice to roll over geology, but every once in a while you have to pull out a shovel, dig a hole and find out what is really underneath your feet,” says Robert Sullivan, senior research associate in space sciences and a planetary geology member of the Mars mission’s science team. He devised the plan with Harry Stewart, Cornell associate professor of civil engineering, and engineers at the Jet Propulsion Laboratory (JPL) in Pasadena.

The researchers perfected a digging method to lock all but one of a rover’s wheels on the Martian surface. The remaining wheel will spin, digging the surface soil down about 5 inches, creating a crater-shaped hole that will enable the remote study of the soil’s stratigraphy and an analysis of whether water once existed. For controllers at JPL, the process will involve complicated maneuvers — a “rover ballet,” according to Sullivan — before and after each hole is dug to coordinate and optimize science investigations of each hole and its tailings pile.

JPL, a division of the California Institute of Technology, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Cornell, in Ithaca, N.Y., is managing the science suite of instruments carried by the two rovers.

Each rover has a set of six wheels carved from aluminum blocks, and inside each wheel hub is a motor. To spin a wheel independently, JPL operators will simply switch off the other five wheel motors. Sullivan, Stewart and Cornell undergraduates Lindsey Brock and Craig Weinstein used Cornell’s Takeo Mogami Geotechnical Laboratory to examine various soil strengths and characteristics. They also used Cornell’s George Winter Civil Infrastructure Laboratory to test the interaction of a rover wheel with the soil. Each rover wheel has spokes arranged in a spiral pattern, with strong foam rubber between the spokes; these features will help the rover wheels function as shock absorbers while rolling over rough terrain on Mars.

In November, Sullivan used JPL’s Martian terrain proving ground to collect data on how a rover wheel interacts with different soil types and loose sand. He used yellow, pink and green sand — dyed with food coloring and baked by Brock. Sullivan used a stack of large picture frames to layer the different colored sands to observe how a wheel churned out sloping tailings piles and where the yellow, pink and green sand finally landed. “Locations where the deepest colors were concentrated on the surface suggest where analysis might be concentrated when the maneuver is repeated for real on Mars,” he says.

Stewart notes similarities between these tests and those for the lunar-landing missions in the late-1960s, when engineers needed to know the physical characteristics of the moon’s surface. Back then, geologists relied on visual observations from scouting missions to determine if the lunar lander would sink or kick up dust, or whether the lunar surface was dense or powdery.

“Like the early lunar missions, we’ll be doing the same thing, only this time examining the characteristics of the Martian soil,” Stewart says. “We’ll be exposing fresh material to learn the mineralogy and composition.”

Original Source: Cornell News Release

Image credit: NASA/JPL

Data gathered by NASA’s Mars Global Surveyor and Mars Odyssey spacecraft show evidence that the Red Planet might be coming out of a recent ice age. Unlike on Earth, an ice age on Mars happens when the poles warm up and water vapour can escape to lower latitudes on the planet. Scientists examined global patterns of landscape shapes and near-surface ice levels and found that a covering of ice and dust covered the surface to latitudes as low as 30 degrees – and it’s currently on the retreat. They believe this ice age happened just 400,000 to 2.1 million years ago.

NASA’s Mars Global Surveyor and Mars Odyssey missions have provided evidence of a relatively recent ice age on Mars. In contrast to Earth’s ice ages, a Martian ice age waxes when the poles warm, and water vapor is transported toward lower latitudes. Martian ice ages wane when the poles cool and lock water into polar icecaps.

The “pacemakers” of ice ages on Mars appear to be much more extreme than the comparable drivers of climate change on Earth. Variations in the planet’s orbit and tilt produce remarkable changes in the distribution of water ice from Polar Regions down to latitudes equivalent to Houston or Egypt. Researchers, using NASA spacecraft data and analogies to Earth’s Antarctic Dry Valleys, report their findings in Thursday’s edition of the journal Nature.

“Of all the solar system planets, Mars has the climate most like that of Earth. Both are sensitive to small changes in orbital parameters,” said planetary scientist Dr. James Head of Brown University, Providence, R.I., lead author of the study. “Now we’re seeing that Mars, like Earth, is in a period between ice ages,” he said.

Discoveries on Mars, since 1999, of relatively recent water- carved gullies, glacier-like flows, regional buried ice and possible snow packs created excitement among scientists who study Earth and other planets. Information from the Mars Global Surveyor and Odyssey missions provided more evidence of an icy recent past.

Head and co-authors from Brown (Drs. John Mustard and Ralph Milliken), Boston University (Dr. David Marchant) and Kharkov National University, Ukraine (Dr. Mikhail Kreslavsky) examined global patterns of landscape shapes and near-surface water ice the orbiters mapped. They concluded a covering of water ice mixed with dust mantled the surface of Mars to latitudes as low as 30 degrees, and is degrading and retreating. By observing the small number of impact craters in those features and by backtracking the known patterns of changes in Mars’ orbit and tilt, they estimated the most recent ice age occurred just 400 thousand to 2.1 million years ago, very recent in geological terms. “These results show Mars is not a dead planet, but it undergoes climate changes that are even more pronounced than on Earth,” Head said.

Marchant, a glacial geologist, who spent 17 field seasons in the Mars-like Antarctic Dry Valleys, said, “These extreme changes on Mars provide perspective for interpreting what we see on Earth. Landforms on Mars that appear to be related to climate changes help us calibrate and understand similar landforms on Earth. Furthermore, the range of microenvironments in the Antarctic Dry Valleys helps us read the Mars record.”

Mustard said, “The extreme climate changes on Mars are providing us with predictions we can test with upcoming Mars missions, such as Europe’s Mars Express and NASA’s Mars Exploration Rovers. Among the climate changes that occurred during these extremes is warming of the poles and partial melting of water at high altitudes. This clearly broadens the environments in which life might occur on Mars.”

According to the researchers, during a Martian ice age, polar warming drives water vapor from polar ice into the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed generously with dust. This ice-rich mantle, a few meters thick, smoothes the contours of the land. It locally develops a bumpy texture at human scales, resembling the surface of a basketball, and also seen in some Antarctic icy terrains. When ice at the top of the mantling layer sublimes back into the atmosphere, it leaves behind dust, which forms an insulating layer over remaining ice. On Earth, by contrast, ice ages are periods of polar cooling. The buildup of ice sheets draws water from liquid- water oceans, which Mars lacks. The age of the Earth, like Mars, is 4.6 billion years.

“This exciting new research really shows the mettle of NASA’s ‘follow-the-water’ strategy for studying Mars,” said Dr. Jim Garvin, NASA’s lead scientist for Mars exploration. “We hope to continue pursuing this strategy in January, if the Mars Exploration Rovers land successfully. Later, the 2005 Mars Reconnaissance Orbiter and 2007 Phoenix near-polar lander will be able to directly follow up on these astounding findings by Professor Head and his team.”

Global Surveyor has been orbiting Mars since 1997, Odyssey since 2001. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages both missions for the NASA Office of Space Science, Washington. Information about NASA’s Mars missions is available on the Internet at: http://mars.jpl.nasa.gov

Original Source: NASA News Release