Mars Exploration Program: Images. Three images of the same location taken at different times on Mars show seasonal activity causing sand avalanches and ripple changes on a Martian dune.
Time sequence of the images progresses from top to bottom. Each image covers an area 285 meters (312 yards) by 140 meters (153 yards). The crest of a dune curves across the upper and left portions of the image. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took these images. The site is at 84 degrees north latitude, 233 degrees east longitude, in a vast region of dunes at the edge of Mars' north polar ice cap.
Spring evaporation of the seasonal layer of ice is manifested as dark streaks of fine particles carried to the top of the ice layer by escaping gas. The top image is a portion of the HiRISE observation catalogued as PSP_008867_2640, taken on June 17, 2008. The middle image is a portion of the HiRISE observation catalogued as ESP_016779_2640, taken on Feb. 23, 2010.
Curiosity rover: Martian solar day 2. How Big is the Entire Universe? “The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.” -Stephen Hawking The Universe is a vast, seemingly unending marvel of existence. Over the past century, we’ve learned that the Universe stretches out beyond the billions of stars in our Milky Way, out across billions of light years, containing close to a trillion galaxies all told. Image credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team. And yet, that’s just the observable Universe! To help us better understand this question, let’s turn to something more familiar (and smaller) that we know how to measure the size of: the Earth. Image credit: Tom of From the top of a tall mountain, like Mauna Kea, shown here, you might hope to measure the Earth’s curvature, but your efforts would be in vain. There are images out there where the Earth appears curved when you look out at the water, and indeed, they’re not hard to find.
Image credit: James Elders of Flatwoods and Lighterknots. What is the universe made of?" Imagine you want to determine the mass of a house and its contents. You pick up the house and set it on a giant scale. Let's say, for argument's sake, you measure the mass to be 100,000 pounds (45,359 kilograms). Now imagine you want to see what each item in the house contributes to the total mass. You remove one item at a time and place it on the scale. You even eliminate all of the air to get a measure of its mass. For the last 40 years, this is exactly the dilemma astronomers have faced as they've tried to determine the building blocks of the universe.