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Five Things About Hurricanes
July 1st, 2009
JPL scientist Bjorn Lambrigtsen goes on hurricane watch every June. He is part of a large effort to track hurricanes and understand what powers them. Lambrigtsen specializes in the field of microwave instruments, which fly aboard research planes and spacecraft, penetrating through thick clouds to see the heart of a hurricane.
While scientists are adept at predicting where these powerful storms will hit land, there are crucial aspects they still need to wrench from these potentially killer storms.
Here are thoughts and factoids from Lambrigtsen in the field of hurricane research.
1. Pinpointing the moment of birth
Hurricane Gustav moved along the southern side of Jamaica on Aug. 29, 2008. Image credit: NASA MODIS Rapid Response
Most Atlantic hurricanes start as a collection of thunderstorms off the coast of Africa. These storm clusters move across the Atlantic, ending up in the Caribbean, Gulf of Mexico or Central America. While only one in 10 of these clusters evolve into hurricanes, scientists do not yet know what triggers this powerful transformation.
Pinpointing a hurricane’s origin will be a major goal of a joint field campaign in 2010 between NASA and the National Oceanic and Atmospheric Administration (NOAA).
2. Predicting intensity
Another focus of next year’s research campaign will be learning how to better predict a storm’s intensity. It is difficult for emergency personnel and the public to gauge storm preparations when they don’t know if the storm will be mild or one with tremendous force. NASA’s uncrewed Global Hawk will be added to the 2010 research armada. This drone airplane, which can fly for 30 straight hours, will provide an unprecedented long-duration view of hurricanes in action, giving a window into what fuels storm intensity.
3. Deadly force raining down
Think about a hurricane. You imagine high, gusting winds and pounding waves. However, one of the deadliest hurricanes in recent history was one that parked itself over Central America in October 1998 and dumped torrential rain. Even with diminished winds, rain from Hurricane Mitch reached a rate of more than 4 inches per hour. This caused catastrophic floods and landslides throughout the region.
4. Replenishing “spring”
Even though hurricanes can wreak havoc, they also carry out the important task of replenishing the freshwater supply along the Florida and southeastern U.S. coast and Gulf of Mexico. The freshwater deposited is good for the fish and the ecological environment.
5. One size doesn’t fit all
Hurricanes come in a huge a variety of sizes. Massive ones can cover the entire Gulf of Mexico (about 1,000 miles across), while others are just as deadly at only 100 miles across. This is a mystery scientists are still trying to unravel.
NASA and NOAA conduct joint field campaigns to study hurricanes. The agencies use research planes to fly through and above hurricanes, and scientists collect data from NASA spacecraft that fly overhead. NOAA, along with its National Hurricane Center, is the U.S. government agency tasked with hurricane forecasting.
For more information on how NASA and JPL study hurricanes, go to www.nasa.gov/hurricane and http://tropicalcyclone.jpl.nasa.gov
Five ‘Holy Grails’ of Distant Solar Systems
June 11th, 2009
Angelle Tanner, a post-doctoral scholar at JPL and Caltech, studies planets in distant solar systems, called extrasolar planets. The golden prize in this field is to find a planet similar to Earth - the only planet we know that harbors life. While more than 350 extrasolar planets have been detected, most are gas planets, with no solid surface. Many are located in orbits closer to their parent star than Mercury is to the sun. In other words, not very similar to Earth.
Here’s Tanner’s short list of what she and her colleagues would love to find in another planet - the elements that might enable life on another world. With the powerful tools scientists have now and with new technology and missions coming soon, the odds are going up for finding an Earth-like planet, if one is out there.
Tanner’s top five “holy grails” of extrasolar planet research are hoped-for findings that she predicts will happen within the next 15 years.
1. First planet that weighs the same as Earth
Artist’s concept of an extraolar planet.
Image credit: NASA/JPL-Caltech
Although most planets discovered have been giant gas planets with no surface, a handful of rocky planets, called super-earths, have also been detected. Super-earths are akin to Earth in their rocky make-up, but with a mass up to 10 times that of Earth.
There is no reason these planets could not host an atmosphere or even life as we know it. The discovery of a true Earth clone – Earth-like in size and make-up — could happen within a year or two. NASA’s recently launched Kepler mission has the ability to find planets as small as Earth.
2. First Earth-sized planet in the ‘habitable zone’
The so-called habitable zone is the area around a star where a rocky planet could have the right temperature to have liquid water on its surface. In our solar system, Earth sits in the habitable zone. Venus sits just inside the habitable zone and is too hot while Mars is just outside and too cold. Finding an Earth-sized planet is this geographically desirable location is the next big step in extrasolar research. One super-earth has already been detected near to its parent star’s habitable zone and it is only a matter of time — using existing technologies –- before a planet is found in this friendly environment. Ground-based telescopes and NASA’s Kepler mission are searching stars within a few hundred light years of Earth right now.
3. First atmosphere on a rocky planet
A planet’s atmosphere, along with other factors, helps determine whether a planet could sustain life. For the past few years, astronomers have studied the atmospheres of Jupiter-like, extrasolar planets. These gas giant planets have hydrogen-rich atmospheres inhospitable to life as we know it. However, many of the techniques developed for studying gas giants could be used to study the atmospheres of super-earths. This would mark an important step in beginning to understand the environment of rocky planets.
4. First hint of habitability and life
Once astronomers have enough Earth-sized planet atmospheres to study, they will be looking for biosignatures – indicators in a planet’s atmosphere that the planet might be hospitable to or even support life. Some of the molecules they will be looking for include water vapor, methane, ozone and carbon dioxide. NASA’s James Webb Space Telescope, scheduled to launch in 2014, will provide scientists with the sophisticated instruments needed for these potential observations on super-earths orbiting small stars. Assuredly, astrobiologists will be studying such data for years to come since potential life may, or may not be, in a form we expect. Keeping an open mind is critical.
5. The unexpected
The final grail — the unexpected. The history of science is marked with findings that were never predicted. As in all fields of science and exploration, it’s what we don’t know that will be the most exciting.
For more information about extrasolar planets, visit planetquest.jpl.nasa.gov
Got Water?
May 19th, 2009
Deputy Project Scientist - Mars Reconnaissance Orbiter
A theme of Mars exploration is “Follow the Water,” since understanding the history of water on our planetary neighbor will help us understand if there were environments favorable for life to occur and how climate has changed over time. This is because all life on Earth requires water and we assume the same applies elsewhere in the universe. The Mars Reconnaissance Orbiter has made numerous discoveries that have provided new insights into past wet environments on Mars, water vapor in the planet’s current atmosphere and ice in the subsurface. However, so far, liquid water remains elusive.
The Shallow Radar, or “SHARAD” instrument is the only one on the Mars orbiter that was designed with a goal of discovering liquid water below Mars’ surface. This ground-penetrating radar instrument, which was supplied by the Italian Space Agency, transmits a radar signal at approximately 20 megahertz, and receives any radar waves that bounce off the surface or subsurface layers. The radar instrument has sufficient strength to see layers to a depth of about one kilometer (a little more than one-half mile), and even deeper in the polar caps. Layers in the subsurface reflect the radar wave if there is sufficient contrast in their dielectric properties (their bulk electrical properties), as for example between dry sand and ice-filled sand. Water is a much better conductor than other geologic materials, and thus should be readily detected if present.
This image from NASA’s Mars Reconnaissance Orbiter shows gully channels in a crater in the southern highlands of Mars.The gullies emanating from the rocky cliffs near the crater’s rim (upper left) show meandering and braided patterns typical of water-carved channels. Image credit: NASA/JPL/University of Arizona
Of all the features believed to be formed by water on Mars, we have found only two gullies known to have recent flows – within the last 5-10 years. Gullies are narrow channels that emanate from cliff walls, starting well below the local ground surface. Dr. Michael Malin used the Mars Orbital Camera on Mars Global Surveyor to repeatedly image these features because of their fresh, unweathered appearance. These efforts led to the discovery of the two relatively new gullies.
To date, the Shallow Radar instrument’s observations of dozens of regions containing gullies show no evidence of liquid water. Since slopes of the cliffs where the two new gullies occur are extremely steep, some scientists put forth an alternate hypothesis in which dry debris tumbling downhill could have formed the latest channels. Yet many of the features observed at these and other gullies strongly suggest that liquid water had at least some role in carving the channels. These channels may have formed when a past climate change caused subsurface ice to melt. Or perhaps liquid water was trapped in a past aquifer. But for now, liquid water, if it exists today on Mars, remains out of reach of the Mars Reconnaissance Orbiter.
(blog question) What if the water is liquefied locally either by local or global environment change (mechanical, temperature, chemical…) thus generating a local and temporary phenomena? In this case it would be extremely difficult to observe liquid water “in action”, but channels presence can still be explained by liquid water flows. As a matter of fact, this hypothesis can be tested by a not so difficult experiment … well, at least for someone having access to the Mars surface
Smrekar says: Hi -
Thanks for comments! Some replys:
One possibility is certainly that something temporarily allows liquid water to
flow. A leading idea is that either warm summer sunshine at just the right
place might allow ice to melt briefly. Enough salt trapped in the ice would
help decrease the melting temperature. Changing climate on Mars can certainly
help make ice deposits unstable. The channels we see may have formed under
past climate conditions, with only dry avalanches forming the recent Œflows¹.
(blog question) The picture you post shows very clear-cut channels. Is there
any info on how much the landscape is changed by the periodic dust storms? I
notice no craters on this landscape, either. So is there any
reason why the channels might not have been cut in, say, the last 10 years?
The winds would surely dry the surface to a good depth quite quickly.
Of course the real (and unfortunately impractical) experiment would be to take
a few gallons of water and spray them on the surface - and sit back and watch
what happens.
Smrekar says:
Hundreds of images are taken each year of gully sites with the hope of seeing
changes. Although we don¹t expect to see anything in action (any liquid water
would sublimate or freeze within an hour or so, depending on the volume) we
are trying to understand the rate at which new gullies form and what are their
characteristics. Several new gully flows have formed in the last 10 years. At
each new site we can calculate determine the shape of the channels, the slope
where they form, monitor changes in color due to dust accumulation, and look
for the presence of unusual composition such as salts. This ongoing study will
help us better understand the role of water.
About This Blog
The JPL Blog seeks to inform and involve the public in the breadth of JPL's missions and projects exploring Earth, Mars, the solar system and the universe beyond. A variety of engineers and scientists contribute posts about the endeavors they are pursuing for NASA and JPL. Selected comments are published and are moderated.
