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.
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.”
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.
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.
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.
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|
|1979-2000 mean||6.70||Sept. 13|
|1981-2010 mean||6.22||Sept. 15|
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.
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 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.
IUCN warns at Hawaii conservation meeting that four of six great ape species are at high risk of extinction
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.
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.
A probe launched by NASA in 2006 has resumed communication with the agency after nearly 23 months of silence.
The STEREO-B spacecraft, which orbits the sun, lost contact with Earth on Oct. 1, 2014.
The Deep Space Network reestablished the link with STEREO-B at 6:21 pm EDT on Sunday.
The long interruption in communication with the spacecraft was most likely the result of a series of events that began with a test of its command loss timer. The device is a kind of automated switch that allows the spacecraft to recover after a hardware failure. It functions by re-setting the hardware if no commands are received for a certain period of time. In STEREO-B’s case, that re-set time was three days.
NASA explained a likely scenario for the communications failure at a website posted shortly after the loss of contact event and still available here. An animated film that provides one possible model for the probe’s communication failure is also available.
STEREO-B’s navigation system probably failed because it was unable to detect guide stars. This caused the probe’s high gain antenna to be pointed away from Earth, which meant that it could not receive a signal. The breakdown in the star tracking system was likely the result of a failed laser.
“Basically, we made a mistake in not accounting for one of those individual lasers failing,” Dr. Joseph Gurman, the STEREO project scientist at NASA’s Goddard Space Flight Center, said. “The data still looked good coming out of the unit as a whole even though one laser was bad. That got us into a situation where the spacecraft was getting bad navigational information.”
STEREO-B remains in an uncontrolled spin, a problem for which there is not currently enough power available to correct. The spacecraft obtains energy by means of solar arrays that extend out from its main section.
Gurman explained that NASA scientists are not sure how much power the probe’s batteries can produce or whether they can be fully re-charged.
“We don’t know if the batteries are damaged,” he said. “We know they can take some charge.”
Whether the spacecraft’s instrumentation is still functional is also unknown.
“I would say that we know nothing about the state of the instruments at this point,” Gurman said.
NASA will proceed cautiously to investigate the STEREO-B probe’s status. What Gurman and his colleagues want to avoid is any command that would return STEREO-B to an uncontrolled spin.
“We have an inertial problem that is giving bad information to the control system on the spacecraft,” he said. “We have to proceed in a step-by-step method.”
The first step will be to figure out the extent to which the probe has, to put it metaphorically, any gas in its tank.
“We have to heat up the probably frozen fuel in the fuel tank,” Gurman explained. “We can proceed from there to use the thrusters to right our attitude by using the autonomy software.”
Gurman is optimistic, though, about the prospects for obtaining more data about the sun from STEREO-B. NASA’s prior experience with another spacecraft that experienced a communication failure – the Solar and Heliospheric Observatory – indicates that instruments can survive with little or no damage, even in the cold of space, for quite some time.
“On SOHO, there were 12 principal investigator experiments,” Gurman said. “Only one mechanism in one telescope was damaged in such a way that we really couldn’t use the instrument. There was one instrument that suffered some degradation. That’s about it. We’re cautiously optimistic that we’ll be able to regain most of the scientific capability, if not all, that we had before.”
In any case, the STEREO mission formally ended eight years ago, so any data obtained from STEREO-B is beyond what was expected at the time of launch.
“Anything we get is gravy, to say the least,” Gurman said.
The probe’s twin, STEREO-A, also revolves around our closest star.
STEREO is an acronym that shortens the twin probes’ formal name – Solar Terrestrial Relations Observatories.
A United Nations agency has predicted that the planet’s recent streak of record-setting hot years will reach a new threshold this year.
The World Meteorological Organization also noted in the July 21 statement that the concentration of atmospheric carbon dioxide has reached “new highs.”
The current level of CO2 in the atmosphere exceeds 400 parts per million, a concentration not known on Earth since the Pliocene epoch, which ended about 1.8 million years ago.
In June the average concentration reached 407 parts per million, which was 4 ppm greater than in June 2015.
A WMO official pointed to the trend as a reason to emphasize public policies aimed at reducing greenhouse gas emissions.
“This underlines more starkly than ever the need to approve and implement the Paris Agreement on climate change, and to speed up the shift to low carbon economies and renewable energy,” Petteri Taalas, the agency’s secretary-general, said.
The WMO statement highlighted a streak of record-setting hot months in its prediction.
NOAA also said that June was the 14th consecutive month to set a heat record.
“Another month, another record,” Taalas said. “And another. And another. Decades-long trends of climate change are reaching new climaxes, fueled by the strong 2015/2016 El Niño.”
WMO also pointed to reduced Arctic sea ice during summer months, increased precipitation in some regions, and widespread bleaching of coral reefs as indicators of the climate trend that is likely to put 2016 in the record books.