Top Stories

Wednesday, October 31, 2012

Cassini Halloween Treat: Titan Glows in the Dark

NASA Hosts Nov. 2 Teleconference About Mars Rover Progress

Tuesday, October 30, 2012

NASA Rover's First Soil Studies Help Fingerprint Martian Minerals

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. PHONE 818-354-5011
http://www.jpl.nasa.gov

Guy Webster / D.C. Agle 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov / agle@jpl.nasa.gov

Rachel Hoover 650-604-4789
NASA Ames Research Center, Moffett Field, Calif.
rachel.hoover@nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

News release: 2012-341 Oct. 30, 2012

NASA Rover's First Soil Studies Help Fingerprint Martian Minerals

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.php?release=2012-341&cid=release_2012-341

PASADENA, Calif. -- NASA's Mars rover Curiosity has completed initial experiments showing the mineralogy of Martian soil is similar to weathered basaltic soils of volcanic origin in Hawaii.

The minerals were identified in the first sample of Martian soil ingested recently by the rover. Curiosity used its Chemistry and Mineralogy instrument (CheMin) to obtain the results, which are filling gaps and adding confidence to earlier estimates of the mineralogical makeup of the dust and fine soil widespread on the Red Planet.

"We had many previous inferences and discussions about the mineralogy of Martian soil," said David Blake of NASA Ames Research Center in Moffett Field, Calif., who is the principal investigator for CheMin. "Our quantitative results provide refined and in some cases new identifications of the minerals in this first X-ray diffraction analysis on Mars."

The identification of minerals in rocks and soil is crucial for the mission's goal to assess past environmental conditions. Each mineral records the conditions under which it formed. The chemical composition of a rock provides only ambiguous mineralogical information, as in the textbook example of the minerals diamond and graphite, which have the same chemical composition, but strikingly different structures and properties.

CheMin uses X-ray diffraction, the standard practice for geologists on Earth using much larger laboratory instruments. This method provides more accurate identifications of minerals than any method previously used on Mars. X-ray diffraction reads minerals' internal structure by recording how their crystals distinctively interact with X-rays. Innovations from Ames led to an X-ray diffraction instrument compact enough to fit inside the rover.

These NASA technological advances have resulted in other applications on Earth, including compact and portable X-ray diffraction equipment for oil and gas exploration, analysis of archaeological objects and screening of counterfeit pharmaceuticals, among other uses.

"Our team is elated with these first results from our instrument," said Blake. "They heighten our anticipation for future CheMin analyses in the months and miles ahead for Curiosity."

The specific sample for CheMin's first analysis was soil Curiosity scooped up at a patch of dust and sand that the team named Rocknest. The sample was processed through a sieve to exclude particles larger than 0.006 inch (150 micrometers), roughly the width of a human hair. The sample has at least two components: dust distributed globally in dust storms and fine sand originating more locally. Unlike conglomerate rocks Curiosity investigated a few weeks ago, which are several billion years old and indicative of flowing water, the soil material CheMin has analyzed is more representative of modern processes on Mars.

"Much of Mars is covered with dust, and we had an incomplete understanding of its mineralogy," said David Bish, CheMin co-investigator with Indiana University in Bloomington. "We now know it is mineralogically similar to basaltic material, with significant amounts of feldspar, pyroxene and olivine, which was not unexpected. Roughly half the soil is non-crystalline material, such as volcanic glass or products from weathering of the glass. "

Bish said, "So far, the materials Curiosity has analyzed are consistent with our initial ideas of the deposits in Gale Crater recording a transition through time from a wet to dry environment. The ancient rocks, such as the conglomerates, suggest flowing water, while the minerals in the younger soil are consistent with limited interaction with water."

During the two-year prime mission of the Mars Science Laboratory Project, researchers are using Curiosity's 10 instruments to investigate whether areas in Gale Crater ever offered environmental conditions favorable for microbial life.

NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the project for NASA's Science Mission Directorate, Washington, and built Curiosity and CheMin.

For more information about Curiosity and its mission, visit: http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl .

For more information about a commercial application of the CheMin technology, visit: http://blogs.getty.edu/iris/mars-rover-technology-helps-unlock-art-mysteries/ .

You can follow the mission on Facebook and Twitter at: http://www.facebook.com/marscuriosity and http://www.twitter.com/marscuriosity .

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Friday, October 26, 2012

NASA Oct. 30 Telecon About Mars Curiosity Progress

Thursday, October 25, 2012

NASA Radar Penetrates Thick, Thin of Gulf Oil Spill

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 PHONE 818-354-5011
http://www.jpl.nasa.gov

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

News release: 2012-337 Oct. 25, 2012

NASA Radar Penetrates Thick, Thin of Gulf Oil Spill

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.php?release=2012-337&cid=release_2012-337

PASADENA, Calif. – Researchers at NASA's Jet Propulsion Laboratory and the California Institute of Technology in Pasadena have developed a method to use a specialized NASA 3-D imaging radar to characterize the oil in oil spills, such as the 2010 BP Deepwater Horizon spill in the Gulf of Mexico. The research can be used to improve response operations during future marine oil spills.

Caltech graduate student Brent Minchew and JPL researchers Cathleen Jones and Ben Holt analyzed NASA radar imagery collected over the main slick of the BP Deepwater Horizon oil spill on June 22 and June 23, 2010. The data were acquired by the JPL-developed Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) during the first of its three deployments over the spill area between June 2010 and July 2012. The UAVSAR was carried in a pod mounted beneath a NASA C-20A piloted aircraft, a version of the Gulfstream III business jet, based at NASA's Dryden Aircraft Operations Facility in Palmdale, Calif. The researchers demonstrated, for the first time, that a radar system like UAVSAR can be used to characterize the oil within a slick, distinguishing very thin films like oil sheen from more damaging thick oil emulsions.

"Our research demonstrates the tremendous potential of UAVSAR to automate the classification of oil in a slick and mitigate the effects of future oil spill tragedies," said Jones. "Such information can help spill incidence response commanders direct cleanup operations, such as the mechanical recovery of oil, to the areas of thick oil that would have the most damaging environmental impacts."

Current visual oil classification techniques are qualitative, and depend upon the skill of the people doing the assessment and the availability of skilled observers during an emergency. Remote sensing allows larger areas to be covered in a consistent manner in a shorter amount of time. Radar can be used at night or in other low-light or poor weather conditions when visual surveys can't be conducted.

Radar had previously been used to detect the extent of oil slicks, but not to characterize the oil within them. It had generally been assumed that radar had little to no use for this purpose. The team demonstrated that UAVSAR could be used to identify areas where thick oil had mixed with the surface seawater to form emulsions, which are mixtures of oil and seawater.

Identifying the type of oil in a spill is vital for assessing its potential harm and targeting response efforts. For example, thin oil consists of sheens that measure from less than 0.0002 inches (0.005 millimeters) to about 0.002 inches (0.05 millimeters) thick. Sheens generally form when little oil is released, as in the initial stages of a spill, or from lightweight, volatile components of spill material. Because sheens contain little oil volume, they weather and evaporate quickly, and are of minor concern from an environmental standpoint. Oil emulsions, on the other hand, are 0.04 inches (1 millimeter) thick, contain more oil, and persist on the ocean surface for much longer, thereby potentially having a greater environmental impact in the open sea and along the shoreline.

"Knowing the type of oil tells us a lot about the thickness of the oil in that area," said Jones.

The researchers acquired data in June 2010 along more than 3,400 miles (5,500 kilometers) of flight lines over an area of more than 46,330 square miles (120,000 square kilometers), primarily along the Gulf Coast. They found that at the time the slick was imaged by UAVSAR, much of the surface layer of the Deepwater Horizon spill's main slick consisted of thick oil emulsions.

UAVSAR characterizes an oil spill by detecting variations in the roughness of its surface and, for thick slicks, changes in the electrical conductivity of its surface layer. Just as an airport runway looks smooth compared to surrounding fields, UAVSAR "sees" an oil spill at sea as a smoother (radar-dark) area against the rougher (radar-bright) ocean surface because most of the radar energy that hits the smoother surface is deflected away from the radar antenna. UAVSAR's high sensitivity and other capabilities enabled the team to separate thick and thin oil for the first time using a radar system.

"We knew we were going to detect the extent of the spill," said Holt. "But we had this great new instrument, so we wanted to see how it would work in this extreme situation, and it turned out to be really unique and valuable, beyond all previous radar results for spills."

"We studied an unprecedented event using data collected by a sophisticated instrument and were able to show that there was a lot more information contained in the data than was apparent when we began," said Minchew. "This is a good example of how the tools of science could be used to help mitigate disasters in real time."

UAVSAR is returning to the Gulf of Mexico area this month and will image the area around the Deepwater Horizon site to look for leaks. In the future, UAVSAR data may be combined with imaging spectroscopic data from JPL's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument to further improve the ability to characterize oil spills under a broader range of environmental conditions.

In addition to characterizing the oil slick, UAVSAR imaged most of the U.S. Gulf of Mexico coastline, extending from the Florida Keys to Corpus Christi, Texas, with extensive inland coverage of the southern Louisiana wetlands around Barataria Bay, the terrestrial ecosystem that ultimately sustained the greatest oiling from the massive spill. Researchers tracked the movement of the oil into coastal waterways and marshlands, monitored impact and recovery of oil-affected wetlands, and assessed how UAVSAR can support emergency responders in future disasters.

UAVSAR is also used to detect detailed Earth movements related to earthquakes, volcanoes and glaciers, as well as for soil moisture and forestry biomass studies. For more on UAVSAR, see: http://uavsar.jpl.nasa.gov/mission_flights.html .

Results of this study are published this month in the Institute of Electrical and Electronics Engineers journal Transactions on Geoscience and Remote Sensing. Caltech manages JPL for NASA.

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NASA's Cassini Sees Burp at Saturn After Large Storm

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 PHONE 818-354-5011
http://www.jpl.nasa.gov

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Elizabeth Zubritsky/Nancy Neal-Jones 301-614-5438/301-286-0039
Goddard Space Flight, Center, Greenbelt, Md.
elizabeth.a.zubritsky@nasa.gov /nancy.n.jones@nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

News release: 2012-335 Oct. 25, 2012

NASA's Cassini Sees Burp at Saturn After Large Storm

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.php?release=2012-335&cid=release_2012-335

PASADENA, Calif. -- NASA's Cassini spacecraft has tracked the aftermath of a rare massive storm on Saturn. Data reveal record-setting disturbances in the planet's upper atmosphere long after the visible signs of the storm abated, in addition to an indication the storm was more forceful than scientists previously thought.

Data from Cassini's composite infrared spectrometer (CIRS) instrument revealed the storm's powerful discharge sent the temperature in Saturn's stratosphere soaring 150 degrees Fahrenheit (83 kelvins) above normal. At the same time, researchers at NASA's Goddard Spaceflight Center in Greenbelt, Md., detected a huge increase in the amount of ethylene gas, the origin of which is a mystery. Ethylene, an odorless, colorless gas, isn't typically observed on Saturn. On Earth, it is created by natural and man-made sources.

Goddard scientists describe the unprecedented belch of energy in a paper to be published in the Nov. 20 issue of the Astrophysical Journal.

"This temperature spike is so extreme it's almost unbelievable, especially in this part of Saturn's atmosphere, which typically is very stable," said Brigette Hesman, the study's lead author and a University of Maryland scientist who works at Goddard. "To get a temperature change of the same scale on Earth, you'd be going from the depths of winter in Fairbanks, Alaska, to the height of summer in the Mojave Desert."

First detected by Cassini in Saturn's northern hemisphere on Dec. 5, 2010, the storm grew so large that an equivalent storm on Earth would blanket most of North America from north to south and wrap around our planet many times. This type of giant disturbance on Saturn typically occurs every 30 Earth years, or once every Saturn year.

Not only was this the first storm of its kind to be studied by a spacecraft in orbit around the planet, but it was the first to be observed at thermal infrared wavelengths. Infrared data from CIRS allowed scientists to take the temperature of Saturn's atmosphere and to track phenomena that are invisible to the naked eye.

Temperature measurements by the composite infrared spectrometer, first published in May 2011, revealed two unusual beacons of warmer-than-normal air shining brightly in the stratosphere. These indicated a massive release of energy into the atmosphere. After the visible signs of the storm started to fade, the instrument's data revealed the two beacons had merged. The temperature of this combined air mass shot up to more than minus 64 degrees Fahrenheit (above 220 kelvins).

According to Hesman, the huge spike of ethylene generated at the same time peaked with 100 times more of the gas than scientists thought possible for Saturn. Goddard scientists confirmed the release of ethylene using the Celeste spectrometer mounted on the McMath-Pierce Solar Telescope on Kitt Peak in Arizona.

The team still is exploring the origin of the ethylene, but has ruled out a large reservoir deep in the atmosphere.

"We've really never been able to see ethylene on Saturn before, so this was a complete surprise," said Goddard's Michael Flasar, the CIRS team lead.

A complementary paper led by Cassini team associate Leigh Fletcher of Oxford University, England, describes how the two stratospheric beacons merged to become the largest and hottest stratospheric vortex ever detected in our solar system. Initially, it was larger than Jupiter's Great Red Spot.

Their paper in the journal Icarus, which combines CIRS data with additional infrared images from other Earth-based telescopes, including NASA's Infrared Telescope Facility at Mauna Kea, Hawaii, also reports a powerful collar of clockwise winds -- encompassing a bizarre soup of gases -- around the vortex.

"These studies will give us new insight into some of the photochemical processes at work in the stratospheres of Saturn, other giants in our solar system, and beyond," said Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate in Washington. Hesman's work was funded in part by NASA's Planetary Astronomy Program in Washington. The CIRS instrument and Celeste spectrometer were built at Goddard. JPL is managed by the California Institute of Technology, Pasadena.

To read more about the Fletcher paper, visit: http://www.esa.int/esaSC/SEMLPIMFL8H_index_0.html .

For information about Cassini and this observation, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

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Wednesday, October 24, 2012

NASA's Spitzer Sees Light of Lonesome Stars

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 PHONE 818-354-5011
http://www.jpl.nasa.gov

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

J.D. Harrington 202-358-5241
NASA Headquarters, Washington
j.d.harrington@nasa.gov

News release: 2012-334 Oct. 24, 2012

NASA's Spitzer Sees Light of Lonesome Stars

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.php?release=2012-334&cid=release_2012-334

PASADENA, Calif. – A new study using data from NASA's Spitzer Space Telescope suggests a cause for the mysterious glow of infrared light seen across the entire sky. It comes from isolated stars beyond the edges of galaxies. These stars are thought to have once belonged to the galaxies before violent galaxy mergers stripped them away into the relatively empty space outside of their former homes.

"The infrared background glow in our sky has been a huge mystery," said Asantha Cooray of the University of California at Irvine, lead author of the new research published in the journal Nature. "We have new evidence this light is from the stars that linger between galaxies. Individually, the stars are too faint to be seen, but we think we are seeing their collective glow."

The findings disagree with another theory explaining the same background infrared light observed by Spitzer. A group led by Alexander "Sasha" Kashlinsky of NASA's Goddard Space Flight Center in Greenbelt, Md., proposed in June this light, which appears in Spitzer images as a blotchy pattern, is coming from the very first stars and galaxies.

In the new study, Cooray and colleagues looked at data from a larger portion of the sky, called the Bootes field, covering an arc equivalent to 50 full Earth moons. These observations were not as sensitive as those from the Kashlinsky group's studies, but the larger scale allowed researchers to analyze better the pattern of the background infrared light.

"We looked at the Bootes field with Spitzer for 250 hours," said co-author Daniel Stern of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Studying the faint infrared background was one of the core goals of our survey, and we carefully designed the observations in order to directly address the important, challenging question of what causes the background glow."

The team concluded the light pattern of the infrared glow is not consistent with theories and computer simulations of the first stars and galaxies. Researchers say the glow is too bright to be from the first galaxies, which are thought not to have been as large or as numerous as the galaxies we see around us today. Instead, the scientists propose a new theory to explain the blotchy light, based on theories of "intracluster" or "intrahalo" starlight.

Theories predict a diffuse smattering of stars beyond the halos, or outer reaches, of galaxies, and in the spaces between clusters of galaxies. The presence of these stars can be attributed to two phenomena. Early in the history of our universe as galaxies grew in size, they collided with other galaxies and gained mass. As the colliding galaxies became tangled gravitationally, strips of stars were shredded and tossed into space. Galaxies also grow by swallowing smaller dwarf galaxies, a messy process that also results in stray stars.

"A light bulb went off when reading some research papers predicting the existence of diffuse stars," Cooray said. "They could explain what we are seeing with Spitzer."

More research is needed to confirm this sprinkling of stars makes up a significant fraction of the background infrared light. For instance, it would be necessary to find a similar pattern in follow-up observations in visible light. NASA's upcoming James Webb Space Telescope (JWST) might finally settle the matter for good.

"The keen infrared vision of the James Webb Telescope will be able to see some of the earliest stars and galaxies directly, as well as the stray stars lurking between the outskirts of nearby galaxies," said Eric Smith, JWST's deputy program manager at NASA Headquarters in Washington. "The mystery objects making up the background infrared light may finally be exposed."

Other authors include Joseph Smidt, Francesco De Bernardis, Yan Gong and Christopher C. Frazer of UC Irvine; Matthew L. N. Ashby of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass; Peter R. Eisenhardt of JPL; Anthony H. Gonzalez of the University of Florida in Gainesville; Christopher S. Kochanek of Ohio State University in Columbus; Szymon Koz?owski of Ohio State and the Warsaw University Observatory in Poland; and Edward L. Wright of the University of California, Los Angeles.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

For more information about Spitzer, visit: http://www.nasa.gov/spitzer .

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Tuesday, October 23, 2012

NASA's NuSTAR Spots Flare From Milky Way's Black Hole

Attend Lunar and Meteorite Sample Certification Workshop at NASA/JPL Educator Resource Center

Educator Workshop Oct. 23, 2012

This is a feature from the NASA/JPL Education Office.

NASA Lunar and Meteorite Sample Certification Program

Date: Saturday, Nov. 10, 2012, 10 a.m. - 12:30 p.m.

Target audience:Recommended for teachers in all grades in a classroom setting

Location: NASA/JPL Educator Resource Center, Pomona, Calif.

Overview: NASA makes actual lunar samples from the historic Apollo missions available to lend to teachers. You must attend this certification workshop to bring the excitement of real lunar rocks and regolith samples to your students. This workshop is being offered at the NASA/JPL Educator Resource Center located in Pomona, please call 909-397-4420 to reserve your spot.

For more information and directions, visit: http://www.jpl.nasa.gov/education/index.cfm?page=115

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Wednesday, October 17, 2012

Could a Hurricane Ever Strike Southern California?

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

News feature: 2012-329 Oct. 17, 2012

Could a Hurricane Ever Strike Southern California?

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.php?release=2012-329&cid=release_2012-329

There's an old adage (with several variations) that California has four seasons: earthquake, fire, flood and drought. While Californians happily cede the title of Hurricane Capital of America to U.S. East and Gulf coasters, every once in a while, Mother Nature sends a reminder to Southern Californians that they are not completely immune to the whims of tropical cyclones. Typically, this takes the form of rainfall from the remnants of a tropical cyclone in the eastern Pacific, as happened recently when the remnants of Hurricane John brought rain and thunderstorms to parts of Southern California. But could a hurricane ever make landfall in Southern California?

The answer, as it turns out, is yes, and no. While there has never been a documented case of a hurricane making landfall in California, the Golden State has had its share of run-ins and close calls with tropical cyclones. In fact, California has been affected by at least a few tropical cyclones in every decade since 1900. Over that timeframe, three of those storms brought gale-force winds to California: an unnamed California tropical storm in 1939, Kathleen in 1976 and Nora in 1997. But the primary threat from California tropical cyclones isn't winds or storm surge. It's rainfall -- sometimes torrential -- which has led to flooding, damage and, occasionally, casualties.

We asked JPL oceanographer and climatologist Bill Patzert about the prospects for future tropical cyclones in Southern California.

Q. We've passed the September peak of hurricane season in the Atlantic and Eastern Pacific Basins -- a year that has been moderately busy for storms thus far. Of course, Southern Californians don't generally think too much about hurricanes. We worry about earthquakes…wildfires…whether the local teams will make the playoffs. But it seems as though every year or so, we get some rain from a tropical cyclone in Southern California. Which begs the question: could a hurricane ever strike here?

Patzert: The interesting thing is that it really can't happen, statistically speaking. The odds are infinitesimal -- so small that everyone should just relax. Like 1 in 1,000. Of course, there's always a chance. But there's a good reason why we don't name our West Coast sports teams the Hurricanes, but we do have the Rancho Cucamonga Quakes.

Seriously, as eastern Pacific hurricanes move northwest and weaken, what we have had are many instances where they dumped a lot of rainfall in Southern California. That's what happened with two monster storms in 1858 and 1939, both El Nino years. And there have been plenty of other examples. When Southern California does get affected by tropical systems, September is by far the most common month.

Q. So why don't we get hurricanes here?

Patzert: There are two main factors that work against hurricanes here: cool waters off the coast and the direction of the upper-level winds.

Tropical cyclones draw their fuel, so to speak, from heat stored in the upper ocean. Typically, ocean surface waters greater than 80 degrees Fahrenheit (27 degrees Celsius) are required to form and fuel these great storms. During the Northern Hemisphere summer and fall, the upper layers of the tropical oceans (down to approximately 330 feet depth) are steadily heated. By September, when hurricane season hits its peak, these waters reach their maximum temperatures, becoming, in a sense, high-octane fuel for hurricanes. But water temperatures never get that high in the coastal waters north of central Baja California. On rare occasions, they may reach about 75 degrees Fahrenheit (24 degrees Celsius) near the shore in Southern California, typically during an El Nino episode. But generally speaking, low 60s is about as warm as they get farther from shore and elsewhere in coastal California.

In the Pacific Ocean, the North Pacific Current flows from Japan eastward across the Pacific and then splits into the northern-flowing Alaska Current and the southern-flowing California Current. The cool-water California Current, which sweeps down the West Coast of the United States, really acts as hurricane repellant, protecting California and even Northern Baja California from hurricanes.

The other factor at play here is the upper-level winds, which tend to carry and steer storms to the west and northwest, away from California, and also tend to shear the tops off of hurricanes, breaking them apart. Between the upper and lower-level winds, there's a lot of wind shear off the coast here in Southern California. These prevailing northwesterly winds also push warmer surface waters offshore, drawing cooler waters up to the surface, and this further adds to the cool nature of the nearby ocean waters that would weaken any storms that did approach California.

Q. But is there a "Perfect Storm" scenario that would allow a tropical cyclone to have a major impact on Southern California?

Patzert: The best odds for a tropical cyclone to affect Southern California are during a "Godzilla" El Nino event, when the waters off the coast are warmest, like we had in 1997-98 when waters were in the low to mid 70s. Or when we're in the positive phase of the Pacific Decadal Oscillation (PDO), a long-term pattern of change in the Pacific Ocean that alternates between cool and warm periods about every five to 20 years. We're currently in the early stages of a cool phase of the PDO, which tends to dampen the effects of El Ninos. Waters in the eastern Pacific generate more hurricanes during El Nino years.

In addition, the upper-level winds would have to steer an unusually strong storm our way. That almost happened with Hurricane Linda in 1997, which briefly threatened Southern California before turning away to sea. But even if Linda had made landfall in California, it wouldn't have been a big wind event. It would have been more like an "atmospheric river" event, common in wintertime, with heavy rainfall and flooding. And storm surge, which is a big concern along the U.S. Gulf and East coasts, is really a negligible issue along most of the California coast, because much of it sits atop bluffs, above sea level.

Q. So how is this hurricane season shaping up in the Pacific and Atlantic?

Patzert: This hurricane season has been moderately active in the eastern Pacific and slightly busier than normal in the Atlantic, but there have been very few big storms. And locally, our current water temperatures off the Southern California coast are between 65 and 70 degrees Fahrenheit [18 and 21 degrees Celsius]. That's way too cold for hurricanes.

Q. Some scientists believe as Earth's climate gets warmer, the frequency and intensity of hurricanes may increase, though the jury is still out on that matter. Do you believe climate change will increase the odds of hurricanes affecting Southern California?

Patzert: Nobody knows yet, and if anybody tells you they know the answer to that question, kick 'em out of your Rolodex file. In fact it's possible that there might be fewer hurricanes in a warming world. But the bottom line for Southern Californians is that even if global temperatures were to rise six degrees, a hurricane in California would rank very low on the list of things we'd need to worry about.

Q. The winter of 1938-39 was something of a freak one for California, with multiple tropical cyclones and other storms affecting the state during the El Nino of 1938-39, resulting in major damage and a large number of fatalities. How have things changed in Southern California in terms of preparation for major storms since then?

Patzert: Anytime you get too much rain too quick, it can cause damage and death, as we saw in the winter of 1938-39. But remember that was before we had a reliable observation network, based on ground and copious satellite measurements, which provided for useful forecasts and warnings. In addition, Southern Californians are flood resistant now because of those storms in 1938-39, which led to all the major rivers here being concreted. So we're largely immunized against these kinds of catastrophic flooding events now.

Q. Do tropical cyclones have a significant impact on Southern California's annual rainfall?

Patzert: In the Southeastern United States, an awful lot of the annual water budget comes from tropical storms, which can have a positive impact as drought busters. But tropical cyclones are not a significant contributor to our rainfall here in Southern California. The average rainfall in Los Angeles in September, even with rainfall from occasional tropical cyclones, is less than half an inch. These amounts are small compared to our normal winter total of 15.1 inches (31 centimeters). But we would certainly welcome any rainfall we can get in September and October, because it can help trump the effects of the hot, dry Santa Ana winds and their associated fire threat. And those are far more real threats to Californians than hurricanes will ever be.

For a brief overview of a few of the more notable tropical cyclones to have affected Southern California in recorded history, visit: http://www.nasa.gov/topics/earth/features/earth20121017.html .

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