NASA’s Modular Robotic Vehicle (MRV), developed at the Johnson Space Center for eventual use off-world, could change how Earthly vehicles drive as well; ‘sideways’ on 4 independent wheel-motors, each of which can rotate 180°. It’s an electric vehicle that can travel up to 62 miles on a charge.
Credit: NASA/JSC
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| An artistic representation of the exoplanet Gliese 832c as compared with Earth. The large planet may be Earth-like, or it could have a dense atmosphere and a closer relationship to Venus. Credit: PHL, University of Puerto Rico, Arecibo |
Long before the hunt began to find Earth lookalikes around other stars, one planet in the solar system had already been named Earth’s twin.
With its similar size and mass, Venus measures very close to Earth, with one major yet significant difference: Its thick atmosphere makes temperatures on the planet hot enough to melt lead, and therefore most certainly too hot to sustain life.
In order to weed out Venus-like planets from those that would be more habitable, several scientists, including planetary scientist Stephen Kaneof San Francisco State University, proposed the establishment of a “Venus zone” around stars, a region where the atmosphere could be consumed by a runaway greenhouse effect that superheats its planets. [Photos of Venus, the Mysterious Planet Next Door]
“We’re specifically trying to make it clear that size is no indication of habitability,” Kane told Astrobiology Magazine.
In other words, just because a planet is roughly the size of Earth, instead of, say, Jupiter, doesn’t guarantee the conditions are right for life to evolve.
The region around a star where liquid water can exist on a planet’s surface is known as the habitable zone. But just because liquid water can exist doesn’t mean that it does. Finding out the conditions on a planet often requires follow-up observations to initial discoveries, but limitations on observation time and equipment mean prioritizing which planets should be the first to be studied in-depth.
“The primary purpose of the habitable zone is target selection,” said Kane.
Kane serves as the chair of NASA’s Kepler Telescope’s Habitable Zone working group, which seeks to utilize all available data from NASA’s Kepler mission, along with any follow-up observations, to provide the most robust list of habitable-zone planets discovered by the telescope. The aim is to better understand how common Earth-size planets are in the habitable zones of other stars. To date, the telescope has identified more than 4,100 planetary candidates.
The Venus zone would similarly serve as a target-selection tool. Scientists hoping to find the next Earth-like planet perform follow-up searches on planetary candidates in the habitable zone; the establishment of a Venus zone would narrow down the inner edge of potential habitability.
A planet within the Venus zone may form an ocean at some point in its history. Indeed, Venus is thought to have harbored wateron its surface until approximately one billion years ago, at which point it lost its liquid.
Kane and his team labeled the point at which a planet would lose its oceansdue to energy from its star as the outer edge of the Venus zone, and the inner boundary of the habitable zone. Losing liquid water would inhibit the carbon cycle of a planet, allowing more to build up in the atmosphere. Rising carbon levels would kick off a runaway greenhouse effect that would heat the planet.
The runaway greenhouse effect for a planet can be avoided if it experiences significant atmospheric loss. As the atmosphere escapes into space, it prevents the carbon from building up and superheating the planet. This loss of atmosphere establishes the inner edge of the Venus zone. [8 Ways Global Warming Is Already Changing the World]
Kane presented his research at the January meeting of the American Astronomical Society in Seattle. The work was also published in Astrophysical Journal Letters.
The majority of the new planetary candidates discovered in recent years has come from NASA’s Kepler telescope. Studying planetary atmospheres, however, continues to be a challenge, one that requires advanced telescopes and the right kind of stars. This situation may change in the future.
“At the moment, we lack enough planets around bright stars, and we lack the resources,” Kane said. “Resources means James Webb.”
Set to launch in 2018, NASA’s James Webb Space Telescopewill be able to search for and study planets around distant stars. At the same time, the agenTransiting Exoplanet Survey Satellite, or TESS, will map exoplanets around the brightest stars in the sky after its 2017 launch.
“James Webb combined with TESSwill really change the game,” Kane said.
Because TESS searches for transiting planets — planets that are observed as they cross their star’s face from the telescope’s perspective — it will be more sensitive to those that orbit closer to their sun.
“TESS will see a lot more exo-Venuses than it will exo-Earths,” planetary atmospheric scientist James Kasting, of Penn State University, told Astrobiology Magazine in an email. “These are the planets to rule out in the search of the more interesting exo-Earths.”
Alien Planet Quiz: Are You an Exoplanet Expert?
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At the same time, studying more exo-Venuses will help to narrow down the line between the Venus zone and the habitable zone, helping scientists to pinpoint which Earth-size planets are Earth twins, and which bear a stronger resemblance to Venus.
“Once we can observe these exo-Venuses and exo-Earths, we’ll be able to determine more accurately the boundary between them,” Kasting said. “Right now, that boundary is based entirely on theoretical climate models, which may not be very accurate under these distinctly non-Earth-like conditions.”
Until then, scientists may have to deal with Venus twins posing as Earth analogues in the samples obtained by Kepler. Kane and his team identified 43 potential Venus analogs, and think that even more exist.
“I suspect a lot of Venus contamination in our sample,” Kane said.
This story was provided by Astrobiology Magazine, a web-based publication sponsored by the NASA astrobiology program. Follow Space.com @Spacedotcom, Facebook and Google+.
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| This photograph of Halley’s Comet was taken Jan. 13, 1986, by James W. Young, resident astronomer of JPL’s Table Mountain Observatory in the San Bernardino Mountains, using a 24-inch reflective telescope. Debris from Halley’s Comet produces the Eta Aquarids meteor shower each May. Credit: NASA/JPL Credit: NASA/JPL |
When asked to name a comet, most people will remember Halley’s. Tonight (May 5), the Eta Aquarid meteor shower, produced by debris from Halley’s Comet, will peak in the night sky, and you can watch live coverage of this Cinco de Mayo meteor shower online.
Late tonight (May 5) and during the early morning hours tomorrow (May 6), skywatchers will have a chance of sighting a few pieces of Halley’s Comet – “comet litter,” if you will – zipping through our atmosphere in the form of meteors. The online Slooh community observatory will host a free webcast of the shower starting at 8 p.m. EDT (0000 GMT) that will stream live at: http://www.slooh.com.
You can also watch the Eta Aquarid webcast live on Space.com, courtesy of Slooh.
The Eta Aquarid meteor shower is predicted to peak on the night of May 5 and into the early morning hours of May 6. Under ideal conditions (a dark, moonless sky) about 40 of these very swift meteors can be seen per hour. The shower appears at about one-quarter peak strength for about three or four days before and after May 6. [See some amazing Eta Aquarid meteor shower photos]
There are, however, two drawbacks if you plan to watch for these meteors this year. First, there is the moon, which was full on Sunday. Although it is now waning (losing illumination), it will still be a bright gibbous phase on the peak morning and will likely “muscle in” on the fainter meteor streaks by brightening the early morning sky with its light.
The other obstacle — at least for those watching from north of the equator — is that the radiant (the emanation point of these meteors) is at the “Water Jar” of the constellation Aquarius, which comes above the southeast horizon around 3 a.m. local daylight time, and never gets very high as seen from north temperate latitudes, so the actual observed rates are usually much lower than the oft-quoted 40 per hour. In North America, typical rates are 10 meteors per hour at 26-degrees north latitude, half this at 35-degrees latitude and practically zero north of 40 degrees.
For most skywatchers, the best hope is catching a glimpse of a meteor emerging from the radiant that will skim the atmosphere horizontally — much like a bug skimming the side window of an automobile. Meteor watchers call such shooting stars “Earthgrazers.” They leave colorful, long-lasting trails.
“These meteors are extremely long,” said Robert Lunsford, of the International Meteor Organization. “They tend to hug the horizon rather than shooting overhead where most cameras are aimed.”
Bill Cooke, a member of the Space Environments team at the Marshall Space Flight Center, said, “Earthgrazers are rarely numerous. But even if you only see a few, you’re likely to remember them.”
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If you do catch sight of tonight’s meteor shower, keep in mind that you’ll likely be seeing the incandescent streak produced by material that originated from the nucleus of Halley’s Comet. When these tiny bits of comet collide with Earth, friction with our atmosphere raises them to a white heat and produces the effect popularly referred to as “shooting stars.”
So it is, that the shooting stars that we have come to call the Eta Aquarids are really an encounter with the traces of a famous visitor from the depths of space and from the dawn of creation.
Halley’s Comet travels around the sun in an elliptical orbit that takes it beyond the orbit of Neptune and as close to the sun as inside the orbit of Venus; a trek that takes roughly 75 years to complete. Halley made its last visit to the sun in 1986 and will return to the vicinity of the sun and Earth in summer 2061.
I’d love to be around to greet Halley when it returns, but that’s not likely to happen. You see, I was 30 years old at its last appearance; I’ll stick to my vitamins and do a lot of good wishing, but . . . well, you do the math. It’s possible, not probable.
And yet, during these next few mornings, both you and I will have a chance of sighting a few pieces of Halley zipping through our atmosphere in the form of meteors.
The orbit of Halley’s Comet closely approaches the Earth’s orbit at two places. One point is in the middle to latter part of October, producing a meteor display known as the Orionids. The other point comes in the early part of May, producing the Eta Aquarids.
Editor’s note: If you snap a photo of an Eta Aqaurid meteor tonight and you’d like to share it with Space.com for a story or image gallery, send images and comments in to: spacephotos@space.com.
Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer’s Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.
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