Drought area in U.S. south now larger than in California

November 30, 2016 Leave a comment

A new map released by the National Drought Mitigation Center presents a shocking image of the country: the area of the south now impacted by drought is larger than the portion of California that is under drought conditions.

Historically anomalous wildfires are currently burning in the Great Smoky Mountains in Tennessee, driven by the dry conditions. The inferno has been driven by high winds, some blowing at velocities in the range of 80-90 miles per hour, and has been burning for four days. The town of Gatlinburg has been significantly damaged by the fires.

Great Smoky Mountains National Park is closed because multiple fires are burning there.

gsmnp-fires-nov-2016
Wildfires are shown in Great Smoky Mountains National Park, Tennessee, Nov. 29, 2016.
Photo courtesy National Park Service.

Altogether, wildfires are burning across at least 95,000 acres in seven southeastern states. According to the National Interagency Fire Center, there are 15 active conflagrations.

NDMC’s weekly report, released Nov. 23, indicates that only Florida and the coastal southeast are experiencing lower-than-average temperatures. A report by the Southeast Regional Climate Center released earlier in November said that precipitation in many parts of the region is running at 30-70 percent of normal. Describing current conditions in the interior southeast, NDMC said that dryness is ubiquitious:

“[H]undreds (at least 212) new fires have started in the Southeast, with 30 of them classified as large wildfires (100 acres or more), and burn bans were widespread across the region. Streams were at record and near-record low levels. Severe agricultural impacts (stock ponds drying up, winter feed being used to keep cattle alive since fall started) were widespread across the South and Southeast.”

us-drought-conidtions-nov-22-2016
This graphic shows U.S. drought conditions as of Nov. 22, 2016.
Graphic by Richard Heim, graphic courtesy National Centers for Environmental Information, National Oceanic & Atmospheric Administration.
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New look at Voyager data indicates that Uranus may have two more moons

October 26, 2016 Leave a comment
uranus-with-rings-and-moons-hubble-space-telescope-courtesy-wikimedia
This Hubble Space Telescope image of Uranus shows the planet surrounded by its four major rings and by 10 of its 27 known satellites. The false-color image was generated by Erich Karkoschka using data obtained by Hubble’s Near Infrared Camera and Multi-Object Spectrometer. Image courtesy NASA, Jet Propulsion Laboratory, Space Telescope Science Institute

Researchers at the University of Idaho say that Uranus, the distant gas giant known for being tipped by 90 degrees, might have two more moons than has previously been thought.

UI physics graduate student Robert O. Chancia and an assistant professor of physics at the university, Dr. Matthew M. Hedman, analyzed data obtained when Voyager 2 transmitted radio waves through Uranus’ rings.

They also looked at changes in the amount of light from distant stars that moves through the planet’s ring system.

Chancia and Hedman found that patterns in the distribution of ring material near the edges of Uranus’ alpha and beta rings vary over time, indicating that small moons may be present.

Dr. Richard G. French, a professor of astrophysics and director of the Whitin Observatory at Wellesley College in Massachusetts, said in an email message that the two UI scientists essentially used a meticulous process of comparison to determine that the pattern was caused by moons.

“Chancia and Hedman compared the wavelike properties from ring profiles taken at slightly different times and different geometries to work backwards to infer the properties of a nearby moon that might produce the satellite wakes,” he wrote.

Hedman pointed out that the results obtained when ground-based receiving stations interpreted the patterns of radio waves after they passed through the two rings shows that the waves were diffracted to varying degrees.

“When you look at this pattern in different places around the ring, the wavelength is different — that points to something changing as you go around the ring,” Hedman said. “There’s something breaking the symmetry.”

The researchers concluded that two possible small moonlets close to Uranus may be the culprits.

“We find for both rings that a moonlet located about 100 [kilometers] exterior to each ring could cause the optical depth variations seen in their occultation scans,” they write in the paper.

French explained that the proposed moons would be quite close to the alpha and beta rings.

“In this case, both moons are slightly exterior to the rings, so they orbit slightly more slowly than the rings themselves,” he wrote in an email message. “As the ring particles pass the moon, their orbits are slightly perturbed, resulting in a ripple pattern within the ring that is detectable as a periodic wavelike structure.”

Those “moonlet wakes” would help to maintain the structure of the Uranian rings, keeping them narrow. The rings are composed of a huge number of tiny particles, which  eventually spread out as collisions between them occur.

Moons near the rings can limit that effect.

French used the example of the planet that may be the solar system’s most famous example of a ring system to explain that a phenomenon called resonance could account for the confining  impact of small moons.

“If you are orbiting Saturn, for example, and you are a little ring particle and you orbit Saturn seven times and the little moon Prometheus six times in that same interval, that’s like getting pushed by the little finger on the swing,” he said. “That little push might be teeny but collectively is powerful. That’s kind of the notion that Matt and his student came up with. Those moons are in the right place to produce this wave pattern inside the rings.”

Chancia said in an email message that he and Hedman are not certain that such moonlet wakes occur in Uranus’ alpha and beta rings.

“We really just wanted to point it out as a possibility, because no one has come up with a universally accepted solution to how these rings are confined,” he wrote. “Anyway, the structures we found look like moonlet wakes.”

If they exist, the two moons would be Uranus’ smallest known and would have a diameter of four to 14 kilometers.

uranus-ring-scheme-courtesy-wikimedia
This diagram shows the Uranian ring scheme. Solid lines depict the rings, while dashed lines indicate the orbital paths of satellites. Graphic courtesy Wikimedia.
uranus-rings-image-courtesy-nasa
This silhouetted image of the rings of Uranus was taken by the Voyager 2 spacecraft on Jan. 24, 1986. A half-second exposure was made with the wide-angle camera at a distance of 63,300 kilometers (39,300 miles). This image shows the nine originally known rings appearing as dark lines against the brighter clouds of the planet. The most prominent ring, called epsilon, appears at the right; barely visible at the left are the three rings known simply as 4, 5 and 6. The resolution of the image is about nine kilometers (five miles). Image courtesy NASA, Jet Propulsion Laboratory.

The proposed moons, if they are there, were not seen by Voyager 2’s cameras. One reason is that the moons are likely so small that the 1970s-vintage equipment could not detect them.

“[G]iven the small predicted sizes of the ∝ and ß moonlets, a convincing detection may not be possible in the Voyager 2 images,” wrote Chancia and Hedman in their paper.

The two newly-hypothesized Uranian moons may also have a very low albedo,  which would make imaging of them difficult. Like the rings to which they are adjacent, they would not reflect much sunlight because the material from which they are constructed is not especially reflective.

“We know that the Uranian rings are dark because we can compare the amount of  light they block during a stellar occultation – a measure of how much material there is in the rings – with how bright they are in reflected sunlight,” French wrote in an email.

“The answer is that they are quite dark – they are not composed of pure water ice, and it’s likely that they are darkened by dust contamination and perhaps by charged particles in the Uranian environment.”

French explained that the two moons proposed by Chancia and Hedman are likely to exhibit the same characteristic.

“If the satellites are dark, too, then they are stealth objects,” he said. “They are also bloody far away.”

Uranus has 27 known moons, all named for literary characters in William Shakespeare’s plays, and 13 rings that have widths between one and 100 kilometers.

The planet’s ring system was discovered in 1977 by ground-based observers using the Kuiper Airborne Observatory.

Voyager 2 was launched in 1977. Voyager 1, a twin outer solar system probe, was sent into space the same year. The latter has now left the solar system and Voyager 2 is likely to do so within the next few years.

The Chancia and Hedman paper is to be published in The Astronomical Journal and appears online at ArXive.

Update, Oct. 26, 2017, 2:42 pm MDT: The word “part” was changed to the word “particle” in a quote by Professor Richard G. French in order to reflect the correct quotation.

NASA says Hubble data indicates possible water plumes on Europa

September 27, 2016 Leave a comment
europa-with-water-vapor-at-7-oclock-position-jan-26-2014-composite-image-image-of-europa-superimposed-on-hubble-data-courtesy-nasa-esa-w-sparks-stsci-usgs-astrogeology-science-center
This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The plumes were photographed by the Hubble Space Telescope Imaging Spectrograph and were seen in silhouette as the moon passed in front of Jupiter. Hubble’s ultraviolet sensitivity allowed for the suspected plumes, which rise at least 160 kilometers above Europa’s icy surface, to be observed. The Hubble STIS data was obtained on Jan. 26, 2014. The image of Europa is superimposed on the Hubble STIS data and was assembled from data gathered during the Galileo and Voyager missions. Image courtesy NASA, European Space Agency, Space Telescope Science Institute/W. Sparks, U.S. Geological Survey Astrogeology Science Center.

NASA announced Monday that scientists using the Hubble Space Telescope have found evidence of water plumes on Europa, which means that spacecraft may be able to explore the moon’s ocean without the need to penetrate its icy surface.

A research team led by astronomer William Sparks of the Space Telescope Science Institute in Baltimore used a technique that has often been instrumental in discovering exoplanets to identify the plumes.

As an exoplanet moves in front of its star, the light from that star changes as it passes through the exoplanet’s atmosphere. This happens because the light encounters a variety of molecules.

europa-transit-illustration-courtesy-a-field-stsci
This image from a STScI animation shows Europa as it transits Jupiter. Animation courtesy Space Telescope Science Institute, animation by A. Field.

On Europa, Sparks and his team noticed that the molecules in the moon’s atmosphere included water vapor. That led them to embark on a quest to determine whether water from Europa’s subsurface ocean is being expelled into space.

The scientists observed Europa pass in front of Jupiter, from which the Sun’s light would be reflected through the atmosphere of the Jovian moon, ten times in 15 months. On three of the occasions water vapor was detected.

“This is an exciting find because it potentially gives us access to the ocean below,” Sparks said at a NASA teleconference on Monday.

Scientists are interested in sampling Europa’s ocean because it may provide indications of whether the moon is, or ever has been, hospitable to life.

“On Earth, life is found wherever there is energy, water, and nutrients, so we have a special interest in any place that has those characteristics,” Dr. Paul Hertz, director of NASA’s astrophysics division in Washington, D.C., said. “Europa might be such a place.”

Europa has a large sub-surface ocean that is thought to contain more water than all of the oceans on Earth. However, the satellite also has a thick icy crust atop that ocean.

The water plumes may rise as high as 200 kilometers off Europa’s surface.

“Europa’s ocean is considered to be one of the most promising places that could potentially harbor life in the solar system,” Geoff Yoder, the acting associate administrator for NASA’s Science Mission Directorate, said. “These plumes, if they do indeed exist, may provide another way to sample Europa’s subsurface.”

A team led by Lorenz Roth of the Southwest Research Institute in Austin, Tex. identified water plumes rising from Europa’s south pole once during 2012.

The Roth group used the Hubble Space Telescope’s Imaging Spectrograph to identify hydrogen and oxygen ions by the ultraviolet radiation they emit after particles accelerated by Jupiter’s magnetic field split water molecules in the Europan atmosphere.

The STScI group also used the STIS instrument, but instead obtained imagery of Europa’s atmosphere in ultraviolet light.

“It’s a technique that complements the Roth team’s,” Dr. Jennifer J. Wiseman, an astrophysicist at NASA’s Goddard Space Flight Center and the agency’s senior scientist assigned to the Hubble Space Telescope, said.

Wiseman explained that STIS’ ultraviolet imaging capacity was particularly helpful to the STScI researchers.

“In ultraviolet light, the surface of Jupiter looks more uniform in color than in visible light, so that allowed the Sparks team to more clearly see the silhouette image of the possible plumes on Europa as the moon passed in front of the smooth Jupiter background,” she wrote in an email message.

The Roth team also used STIS during their quest for Europa’s plumes in 2012.

Sparks said that, notwithstanding a different methodology of investigation, the STScI results are similar to those found by Roth and his colleagues.

“When we calculate in a completely different way the amount of material that would be needed to create these absorption features, it’s pretty similar to what Roth and his team found,” he explained. “The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work.”

comparison-of-2014-transit-and-2012-europa-aurora-observations-transit-on-left-lorenz-roth-team-image-on-right-courtesy-nasa-esa-w-sparks-left-image-l-roth-right-image
These images compare the 2014 transit observed by the STSI team (left) and the 2012 spectroscopy obtained by the Roth team (right). Images courtesy NASA, European Space Agency, W. Sparks (left), L. Roth (right).

The STScI and Roth teams have not seen plumes erupting from Europa at the same times. Sparks and his colleagues observed what they believe to be water plumes in January, March, and April, 2014.

Wiseman said that detection of Europa’s plumes is difficult.

“Such plumes would be faint, probably intermittent, and the ultraviolet wavelengths of light being observed are at the high frequency edge of what Hubble can detect,” she wrote in an email message.

Sparks explained that he and his team do not claim that their work proves the plumes’ existence, though he also said Monday that he does not believe that any other explanation for the findings his team made is likely.

“In a formal sense, we have a statistically significant result,” Sparks said. “The problem is that there may be something we don’t understand about the instrument or the scene. It’s more of a subjective uncertainty than a quantitative uncertainty.”

“I’m not aware of any other plausible natural explanation for the appearance of these patches of absorption,” he continued.

Two of the water plumes that were apparently observed by Sparks and his team occurred near the south pole of Europa and one was seen near the moon’s equator.

A paper detailing the findings by the STScI team will be published in the Sept. 29 edition of Astrophysical Journal.

Saturn’s moon Enceladus is the only body in the solar system known to eject water vapor to space.

Imagery obtained by the Galileo spacecraft during the late 1990s indicated that Europa has an ocean. Observation of the moon’s magnetic fields confirmed its existence.

Wiseman said during Monday’s teleconference that NASA plans to use the James Webb Space Telescope, due to be launched in 2018, to further investigate the possible water plumes of Europa.

james-webb-space-telescope-to-launch-in-2018-courtesy-nasa
The James Webb Space Telescope will be launched in 2018. Artist’s conception courtesy NASA.

In addition, the European Space Agency’s Jupiter Icy Moon Mission (JUICE) and NASA’s planned Europa orbiter will have future opportunities to explore the Jovian satellite.

NOTE 1: This post was updated at 5:38 pm MDT on Sept. 27, 2016 to add a discussion of Dr. Jennifer Wiseman’s interview responses.

NOTE 2: This post was updated at 9:32 pm MDT on Sept. 27, 2016 to correct an inaccurate statement contained in the headline, correct several minor errors in the quotation of Dr. Jennifer Wiseman’s email communication, and correct the acronym applicable to the Space Telescope Science Institute.

NOTE 3: This post was updated at 9:37 pm MDT on Sept. 27, 2016 to clarify the difference between the Roth team’s use of the Hubble Space Telescope’s Imaging Spectrograph in 2012 and the STScI team’s use of that instrument in 2014.

Arctic sea ice reaches lowest extent of year

September 16, 2016 Leave a comment

The amount of summer sea ice in the Arctic fell this year to the second-lowest ever recorded by satellite.

NASA and the National Snow and Ice Data Center in Boulder, Colo. announced Thursday that the Arctic has reached its summer season low extent.

The 4.14 million square kilometers of ice measured on Sept. 10 is statistically tied with the minimum ice extent during the summer of 2007 for second place on the historic minimum list. This year’s minimum ice cover is more than two million square kilometers below the 1981-2010 mean.

Arctic Summer Minimum Sea Ice Extent Record, 2007-2016

YEAR EXTENT (millions of km2) DATE MEASURED
2012 3.39 Sept. 17
2016 4.14 Sept. 10
2007 4.15 Sept. 18
2011 4.34 Sept. 11
2015 4.43 Sept. 9
2008 4.59 Sept. 20
2010 4.62 Sept. 21
2014 5.03 Sept. 17
2013 5.06 Sept. 13
2009 5.12 Sept. 13
1979-2000 mean 6.70 Sept. 13
1981-2010 mean 6.22 Sept. 15
sea-ice-graph-sept-12-2016-graphic-courtesy-national-snow-and-ice-data-center
This graphic shows the minimum Arctic sea ice extent (according to a preliminary assessment) with the seasonal minimum in prior years. Graphic courtesy National Snow and Ice Data Center.

A statement released by NSIDC starkly described the conditions in the Arctic this summer:

“This year’s minimum extent is 750,000 square kilometers (290,000 square miles) above the record low set in 2012 and is well below the two standard deviation range for the 37-year satellite record.”

Cloudy skies and atmospheric pressure conditions slowed ice melt in June and July, which may have prevented this season from becoming the most ice-free summer ever observed from space.

“June and July are usually key months for melt because that’s when you have 24 hours a day of sunlight – and this year we lost melt momentum during those two months,” Walt Meier, a scientist at NASA’s Goddard Space Flight Center, said in a statement.

2016-arctic-sea-ice-minimum-sept-10-graphic-courtesy-nasa-goddard-space-center-visualization-studio-graphic-by-c-starr
This graphic shows the 2016 seasonal minimum, reached on Sept. 10, in comparison with the 1981-2010 average (shown by the gold-colored line). Graphic courtesy NASA Goddard Space Flight Center Scientific Visualization Studio; graphic by C. Starr.

The pace of melting accelerated in August when two cyclones crossed the Arctic Ocean.

Meier explained that these may have especially impacted the speed with which ice in the Chukchi and Beaufort seas melted.

The three-and-one-half decade long satellite record shows a marked decline in the mean extent of Arctic sea ice during each month of the year.

In fact, a paper published on Sept. 15 in the journal Remote Sensing of Environment concluded that no record for maximum Arctic sea ice extent has been set since 1986, while during the 37 years of satellite monitoring there have been 75 new minimum ice extent records set.

“The record makes it clear that the ice is not rebounding to where it used to be, even in the midst of winter,” Claire Parkinson, the lead author of that study and a senior climate scientist at GSFC, said.

Arctic sea ice ordinarily reaches its maximum reach for the year in March, late in the winter. The sun is not visible in the region during the winter and does not contribute much to warming of land and sea surfaces during that season.

NSIDC’s statement cautioned that the estimate released Thursday could be revised if late-summer winds or other factors causing ice melt impact the sea ice cover during the remaining days of summer.

The monitoring record dates to 1978.

Earth’s poles are the two regions of the planet that are most sensitive to warming of the atmosphere. As sea ice melts, more solar energy is absorbed by the Arctic Ocean. The deep and dark waters absorb about 90 percent of the sun’s energy that reaches them.

By contrast, expansion of sea ice during the colder autumn and winter months causes about 80 percent of the solar energy that hits the frozen surface of the region’s marine environment to be reflected to space.

 

August ties July for hottest month ever recorded, says NASA

September 12, 2016 Leave a comment
aug-2016-temperatures
This graphic shows deviations around the world from the 1951-80 mean temperature. Graphic courtesy NASA Goddard Institute for Space Studies.

August 2016 was the warmest month in recorded history, tying July 2016 for that distinction.

NASA said Monday that the mean worldwide temperature during August was 0.16 degrees Celsius hotter than the previous record-setting August and 0.98 degrees Celsius hotter than the average August between 1951-1980.

According to analysis completed by the agency’s Goddard Institute for Space Studies, August 2016 was the eleventh month in a row to reach a new high for that month’s average worldwide temperature.

gistemp-anomaly-aug-2016-v2
This graphic provides another visual indication of the worldwide temperature anomaly in August. Graphic by Gavin Schmidt, courtesy NASA Goddard Institute for Space Studies.

IUCN warns at Hawaii conservation meeting that four of six great ape species are at high risk of extinction

September 6, 2016 Leave a comment

The International Union for Conservation of Nature added the Eastern lowland gorilla (Gorilla berengei) to its list of critically endangered species Sunday, raising the number of great ape species that are on very cusp of extinction to four.

The three other critically endangered species of great apes are the Western gorilla (Gorilla gorilla), Bornean orangutan (Pongo pygmaeus), and Sumatran orangutan (Pongo abelii).

There are six species of great apes. The other two species – the chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus) – are endangered.

G. berengei includes two subspecies. One of them, Grauer’s gorilla (G.b. graueri), has experienced a decline in population of nearly 80 percent since 1994. There are about 3,800 individuals left. The other, the Mountain gorilla (G.b. beringei), has a population of about 880 individuals.

“To see the Eastern gorilla – one of our closest cousins – slide towards extinction is truly distressing,” Inger Anderson, IUCN’s director general, said in a statement. “We live in a time of tremendous change and each IUCN Red List update makes us realize just how quickly the global extinction crisis is escalating.”

The great apes are man’s closest relatives in the natural world.

Chimpanzees and bonobos share about 98.8 percent of the human genome. Gorilla genes are about 98.4 percent identical to humans, while the orangutan genome is about 97 percent identical to man.

The IUCN announcement came at its annual conservation congress, a gathering of political leaders, conservationists, and others, in Honolulu, Hawaii.

U.S. agencies: July is hottest month in recorded history

August 26, 2016 Leave a comment
Land and Sea Surface Anomalies, July 2016

This graphic shows blended air and sea surface temperature anomalies around the world for July 2016. Temperature data is shown in degrees Celsius. Graphic courtesy NOAA National Centers for Environmental Information.

The records kept falling as July 2016 set new benchmarks for heat.

NASA said Aug. 16 that last month was not only the hottest July in recorded history, but also the hottest month known since temperature record-keeping began in 1880.

“It wasn’t by the widest of margins, but July 2016 was the warmest month since modern record keeping began in 1880,” Dr. Gavin Schmidt, director of the agency’s Goddard Institute for Space Studies, said. “It appears almost a certainty that 2016 also will be the warmest year on record.”

This July’s mean temperature was 0.1 degrees warmer than the previous July record holders that occurred in 2015, 2011, and 2009, according to NASA’s study.

The National Oceanic & Atmospheric Administration confirmed July’s status as the heat pacesetter for all months on Aug. 17.

NOAA said that July 2016 was 1.57 degrees Fahrenheit warmer than the average 20th century July and 0.11 degrees Fahrenheit above the previous record-holding month of July 2015.

That continued a decades-long trend for the month of the year that is the peak of summer in the northern hemisphere.

“July 2016 marks the 40th consecutive July with temperatures at least nominally above the 20th century average,” NOAA’s National Centers for Environmental Information said in a summary of the July temperature data. “July 1976 was the last time July global land and ocean temperatures were below average.”

The trend is not limited to every year’s July.

A new record for the warmest month of its kind has been set in each of the past ten months, according to NASA, dating back to October 2015.

NOAA pegged the hot streak at 15 record-setting months in a row.

The disparity is the result of differing methodologies used by the two agencies.

For the year of 2016 through the end of July, NOAA found that mean worldwide temperatures were 1.85 degrees Fahrenheit above the 20th century average.

The next-hottest January-July period came in 2014, when the average was 0.34 degrees F below this year’s measurement.

Both agencies use meteorological stations around the world to obtain air temperature data and ship- and buoy-based instruments to measure sea surface temperature. Antarctic research stations are also used to gather the data that underlies their monthly global temperature analysis reports.

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