NASA is ending attempts to regain contact with the long-lived Mars Exploration Rover Spirit, which last communicated on March 22, 2010.
A transmission that will end on Wednesday, May 25, will be the last in a series of attempts. Extensive communications activities during the past 10 months also have explored the possibility that Spirit might reawaken as the solar energy available to it increased after a stressful Martian winter without much sunlight. With inadequate energy to run its survival heaters, the rover likely experienced colder internal temperatures last year than in any of its prior six years on Mars. Many critical components and connections would have been susceptible to damage from the cold.
Engineers' assessments in recent months have shown a very low probability for recovering communications with Spirit. Communications assets that have been used by the Spirit mission in the past, including NASA's Deep Space Network of antennas on Earth, plus two NASA Mars orbiters that can relay communications, now are needed to prepare for NASA's Mars Science Laboratory mission. MSL is scheduled to launch later this year.
"We're now transitioning assets to support the November launch of our next generation Mars rover, Curiosity," said Dave Lavery, NASA’s program executive for solar system exploration. "However, while we no longer believe there is a realistic probability of hearing from Spirit, the Deep Space Network may occasionally listen for any faint signals when the schedule permits."
Spirit landed on Mars on Jan. 3, 2004, for a mission designed to last three months. After accomplishing its prime-mission goals, Spirit worked to accomplish additional objectives. Its twin, Opportunity, continues active exploration of Mars.
NASA Concludes Attempts to Contact Mars Rover Spirit
NASA's Kepler Spacecraft Discovers Extraordinary New Planetary System
Scientists using NASA's Kepler, a space telescope, recently discovered six planets made of a mix of rock and gases orbiting a single sun-like star, known as Kepler-11, which is located approximately 2,000 light years from Earth.
"The Kepler-11 planetary system is amazing," said Jack Lissauer, a planetary scientist and a Kepler science team member at NASA's Ames Research Center, Moffett Field, Calif. "It’s amazingly compact, it’s amazingly flat, there’s an amazingly large number of big planets orbiting close to their star - we didn’t know such systems could even exist."
In other words, Kepler-11 has the fullest, most compact planetary system yet discovered beyond our own.
"Few stars are known to have more than one transiting planet, and Kepler-11 is the first known star to have more than three," said Lissauer. "So we know that systems like this are not common. There’s certainly far fewer than one percent of stars that have systems like Kepler-11. But whether it’s one in a thousand, one in ten thousand or one in a million, that we don’t know, because we only have observed one of them."
All of the planets orbiting Kepler-11, a yellow dwarf star, are larger than Earth, with the largest ones being comparable in size to Uranus and Neptune. The innermost planet, Kepler-11b, is ten times closer to its star than Earth is to the sun. Moving outwards, the other planets are Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and the outermost planet, Kepler-11g, which is twice as close to its star than Earth is to the sun.
"The five inner planets are all closer to their star than any planet is to our sun and the sixth planet is still fairly close," said Lissauer.
If placed in our solar system, Kepler-11g would orbit between Mercury and Venus, and the other five planets would orbit between Mercury and our sun. The orbits of the five inner planets in the Kepler-11 planetary system are much closer together than any of the planets in our solar system. The inner five exoplanets have orbital periods between 10 and 47 days around the dwarf star, while Kepler-11g has a period of 118 days.
"By measuring the sizes and masses of the five inner planets, we have determined they are among the smallest confirmed exoplanets, or planets beyond our solar system," said Lissauer. "These planets are mixtures of rock and gases, possibly including water. The rocky material accounts for most of the planets' mass, while the gas takes up most of their volume."
According to Lissauer, Kepler-11 is a remarkable planetary system whose architecture and dynamics provide clues about its formation. The planets Kepler-11d, Kepler-11e and Kepler-11f have a significant amount of light gas, which Lissauer says indicates that at least these three planets formed early in the history of the planetary system, within a few million years.
A planetary system is born when a molecular cloud core collapses to form a star. At this time, disks of gas and dust in which planets form, called protoplanetary disks, surround the star. Protoplanetary disks can be seen around most stars that are less than a million years old, but few stars more than five million years old have them. This leads scientists to theorize that planets which contain significant amounts of gas form relatively quickly in order to obtain gases before the disk disperses.
The Kepler spacecraft will continue to return science data about the new Kepler-11 planetary system for the remainder of its mission. The more transits Kepler sees, the better scientists can estimate the sizes and masses of planets.
"These data will enable us to calculate more precise estimates of the planet sizes and masses, and could allow us to detect more planets orbiting the Kepler-11 star," said Lissauer. "Perhaps we could find a seventh planet in the system, either because of its transits or from the gravitational tugs it exerts on the six planets that we already see. We’re going to learn a fantastic amount about the diversity of planets out there, around stars within our galaxy."
A space observatory, Kepler looks for the data signatures of planets by measuring tiny decreases in the brightness of stars when planets cross in front of, or transit, them. The size of the planet can be derived from the change in the star's brightness. The temperature can be estimated from the characteristics of the star it orbits and the planet's orbital period.
The Kepler science team is using ground-based telescopes, as well as the Spitzer Space Telescope, to perform follow-up observations on planetary candidates and other objects of interest found by the spacecraft. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which of the candidates can be identified as planets.
Kepler will continue conducting science operations until at least November 2012, searching for planets as small as Earth, including those that orbit stars in the habitable zone, where liquid water could exist on the surface of the planet. Since transits of planets in the habitable zone of solar-like stars occur about once a year and require three transits for verification, it is predicted to take at least three years to locate and verify an Earth-size planet.
"Kepler can only see 1/400 of the sky," said William Borucki of NASA’s Ames Research Center, Moffett Field, Calif., and the mission’s science principal investigator. "Kepler can find only a small fraction of the planets around the stars it looks at because the orbits aren’t aligned properly. If you account for those two factors, our results indicate there must be millions of planets orbiting the stars that surround our sun."
Kepler is NASA's tenth Discovery mission. Ames is responsible for the ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., managed the Kepler mission development. Ball Aerospace and Technologies Corp., Boulder, Colo., was responsible for developing the Kepler flight system, and along with the Laboratory for Atmospheric and Space Physics at the University of Colorado, is supporting mission operations. Ground observations necessary to confirm the discoveries were conducted at the Keck I in Hawaii; Hobby-Ebberly and Harlan J. Smith 2.7m in Texas; Hale and Shane in California; WIYN, MMT and Tillinghast in Arizona, and the Nordic Optical in the Canary Islands, Spain.
A First Look at Flight in 2025
In late 2010, NASA awarded contracts to three teams — Lockheed Martin, Northrop Grumman, The Boeing Company — to study advanced concept designs for aircraft that could take to the skies in the year 2025.
At the time of the award, the team gave NASA a sneak peek of the particular design they plan to pursue.
Each design looks very different, but all final designs have to meet NASA's goals for less noise, cleaner exhaust and lower fuel consumption. Each aircraft has to be able to do all of those things at the same time, which requires a complex dance of tradeoffs between all of the new advanced technologies that will be on these vehicles.
The proposed aircraft will also have to operate safely in a more modernized air traffic management system.
And each design has to fly up to 85 percent of the speed of sound; cover a range of approximately 7,000 miles; and carry between 50,000 and 100,000 pounds of payload, either passengers or cargo.
For the rest of this year, each team will be exploring, testing, simulating, keeping and discarding innovations and technologies to make their design a winner.
How different will the final designs look from these initial glimpses?
