UNPRECIDENTED 155-MILE HIGH PLUME SEEN OVER MARS
Mysterious plumes above the surface of Mars have scientists stumped. Updated on 3/1/2015.
Mystery Plume on Mars
Figure 1 above has an image was taken on March 20, 2012 by W. Jaeschke. Had it been taken after August 6 that year we would have had weather data from the Mars Science Laboratory, however we still can say this much. The North Pole is at the bottom of the picture, Mars was at Solar Longitude (Ls) 85.4, Sol, 184. This was late spring in the northern hemisphere, late fall in the southern hemisphere below the cloud.
Figure 2 above shows the plume in question in March to April 2012. Figure 3 below shows a lower plume in 1997.
Mystery Plume on Mars
6 February 2015
Plumes seen reaching high above the surface of Mars are causing a stir among scientists studying the atmosphere on the Red Planet.
On two separate occasions in March and April 2012, amateur astronomers reported definite plume-like features developing on the planet.
The plumes were seen rising to altitudes of over 250 km above the same region of Mars on both occasions. By comparison, similar features seen in the past have not exceeded 100 km.
“At about 250 km, the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,” says Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain, lead author of the paper reporting the results in the journal Nature.
The features developed in less than 10 hours, covering an area of up to 1000 x 500 km, and remained visible for around 10 days, changing their structure from day to day.
None of the spacecraft orbiting Mars saw the features because of their viewing geometries and illumination conditions at the time.
However, checking archived Hubble Space Telescope images taken between 1995 and 1999 and of databases of amateur images spanning 2001 to 2014 revealed occasional clouds at the limb of Mars, albeit usually only up to 100 km in altitude.
ROFFMAN COMMENT: The altitude of this event does appear to be a record, however, as we discuss in Section 10.1 of our Report entitled Mars Correct: Critique of All NASA Mars Weather Data, With Emphasis on Pressure:
10.1 Mars Global Surveyor (MGS).
When MGS was launched in 1996, the intent was to achieve a circular pole-to-pole, Sun-synchronous orbit around Mars with an altitude of approximately 300 km above the surface and an orbital period of just under 2 hours. In an attempt to accomplish this orbit using minimal fuel, MGS used aerobraking. It was deliberately flown through the upper atmosphere of Mars during periapse to use the aerodynamic drag forces to modify its orbital parameters. The effort did not go as planned and the early maneuvers led to excessive decelerations (Read & Lewis 2004, 11).78
If Mars has a higher than expected atmospheric density, it would explain unexpected excessive decelerations. As shown in Figure 38 and discussion below, it is believed that a dust storm produced the unexpected drag, but the effects at a normalized altitude of 121 km (75 miles) seem quite high for a planet that is supposed to have an average surface pressure of only about 6.1 mbar.
Johnston et al. (1998)81 reported that (1) “On the onset of a dust storm, the atmospheric density could more than double in a 48 hour time period,” (see Figure 4 below) and (2) “If during aerobraking, the spacecraft experiences dynamic pressure values greater than this limit line, the periapsis altitude of the orbit must be raised immediately in order to re-establish the 90% atmospheric density capability.” Both happened.
Note the tremendous increase in dynamic pressure shown on Figure 38. At an altitude normalized to 121 km, the dust storm caused dynamic pressure to rise from about 0.15 N/m2 on November 9th, 1997 to 0.84 N/m2 on December 7, 1997. While the Johnson et al. (1998) article referred to atmospheric density more than doubling during a dust storm, the increase in dynamic pressure felt at 121 km over four weeks was 5.6 times the pre-storm values.
References for the above can be found on our site here.
But one set of Hubble images from 17 May 1997 revealed an abnormally high plume, similar to that spotted by the amateur astronomers in 2012.
Scientists are now working on determining the nature and cause of the plumes by using the Hubble data in combination with the images taken by amateurs.
“One idea we’ve discussed is that the features are caused by a reflective cloud of water-ice, carbon dioxide-ice or dust particles, but this would require exceptional deviations from standard atmospheric circulation models to explain cloud formations at such high altitudes,” says Agustin.
“Another idea is that they are related to an auroral emission, and indeed auroras have been previously observed at these locations, linked to a known region on the surface where there is a large anomaly in the crustal magnetic field,” adds Antonio Garcia Munoz, a research fellow at ESA’s ESTEC and co-author of the study.
The jury is still out on the nature and genesis of these curious high-altitude Martian plumes. Further insights should be possible following the arrival of ESA’s ExoMars Trace Gas Orbiter at the Red Planet, scheduled for launch in 2016.
Notes for Editors
“An extremely high altitude plume seen at Mars morning terminator,” by A. Sánchez-Lavega et al. is published in the 16 February 2015 issue of the journalNature.
The ground-based images were provided by astronomers W. Jaeschke, D. Parker, J. Phillips and D. Peach.
For further information, please contact:
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Universidad del País Vasco UPV/EHU
Antonio Garcia Munoz
Figure 4 - Actual Dynamic Pressure – Normalized to an Altitude of 121 km (reproduced from Johnson, et al, 1998)
PLUME LOCATION AND CYCLIC BEHAVIOR: The occurrence in March and April 2012 of two bright, extremely high-altitude plumes at the Martian terminator (the day–night boundary) at 200 to 250 kilometers or more above the surface, and thus well into the ionosphere and the Exosphere 8,9. They were spotted at about 24° South, 195° West (at Terra Cimmeria), extended about 500 to 1,000 kilometers in both the north–south and east–west directions, and lasted for about 10 days.The 20 to 21 March observations indicate that the plume feature extended from mean latitude 38.8° South +/-6.4° to 49.7° South +/- 4.2° (~460 km) with extremes from the mean ranging from 32.3° South to 53.9° South. Its longitude varied from 190.2° West +/- 4.2° to 201.4° West +/- 6.8° with extremes from 186° West to 208.2° West°. The features exhibited day-to-day variability, and were seen at the morning terminator but not at the evening limb, which indicates rapid evolution in less than 10 hours and a cyclic behavior.
8. Strobel, D. F. in Atmospheres in the Solar System: Comparative Aeronomy (eds Mendillo, M., Nagy, A. & Waite, J. H.) 39–54, 191–202 (American Geophysical Union, 2002).
9. Yagi, M. et al. Mars exospheric thermal and non-thermal
Discussion about the location. The closest lander that has been sent to this part of the planet was the Spirit Rover which touched down at about 14.8° South, 184.5° West at Gusev Crater. The Spirit mission ended in May 25, 2011, about 10 months before the plumes were seen.
Discussion about the cyclic nature of the cloud. What are we to make of the statement that "the features exhibited day-to-day variability, and were seen at the morning terminator but not at the evening limb, which indicates rapid evolution in less than 10 hours and a cyclic behavior?" Does anything else have such a short period on Mars? While the gravity of the Martian moon Phobos is quite low, the moon (just 3,700 miles/6,000 km miles up) orbits the planet in only 7 hours 39.2 minutes. Because it orbits the planet faster than than Mars rotates, the moon appears to rise in the west and set in the east twice every Martian day. Phobos is small (27 X 22 X 18 km), and the escape velocity is only 11.39 meters per second. Could the small gravitational tug affect the molecules in the cloud seen? This would require a lot to prove, not the least of which is how much less than 10 hours it took to have the cloud disappear each Martian day (sol).
Two scenarios advanced by A. Sanchez-Lavega (et al. 2015).
The first involves H2O-ice, CO2-ice or dust. They ruled out dust for the 1997 event and found only marginal agreement in 2012 with Mie theory and wavelength-dependent indices of refraction. The best fit was for CO2 or H2O ice particles with effective radii of 0.1+0.1 to -0.0004 microns. This they indicate was consistent with the size of mesospheric clouds observed at night (Montmessin, F. et al. Hyperspectral imaging of convective on convective CO2 ice clouds in the equatorial mesosphere of Mars. J. Geophys. Res. 112, 11S90 (2007).
Water condensation at the relevant altitude requires either anomalously cold thermosphere (with temperature drop >50 K or a unusual water mixing from 10-4 to complete saturation above 140 km. Carbon dioxide condensation would require would require an even larger temperature drop of 100 K above 125 km. But explaining the cloud would require vigorous vertical transport up to at least 180 km above the surface under high insolation likely to occur at noon. But the cloud was not visible at that that time of day. Bottom line, these even are difficult to support.
The second idea is that the 2012 plume might be due to an aurora. Martian aurora have been seen near where the plume occurs, a region with a large anomaly in the crustal magnetic field (175° West) that can drive solar wind particles into the atmosphere. However, this hypothesis requires an exceptionalninflux of energetic particles over days, but solar activity in March 2012 was not unusally high. Further, extrapolation from ultraviolet intensies to visible falls short of reported plume brightness by orders of magnitude.
COULD DUST KICKED UP BE CAUSED BY WHAT CAUSED MARTIAN FLARES - ASTEROID IMPACTS OR VOLCANOES?
The plumes up to 155 mile high were not caused by asteroid impacts. We can say that because of their regular occurence at the same time over many days. However, asteroid impacts might explain earlier bright spots seen on Mars seen by telescopes on Earth.
A friend of our family and former (controversial) NASA employee, Clark McClelland claimed to witness a flash on Mars, via the 13 inch Fitz-Clark refractor telescope at the Allegheny Observatory back in 1954. He also sent us an article about Tsuneo Saheki of the Osaka Planetarium who was viewing a 5.3 inch disc of Mars through an 8 inch Newtonian telescope at 400 power. Saheki claimed to see a a very small, extremely bright spot appear at 2100 Universal time on December 8, 1951. While Clark thought he was witnessing a volcanic eruption in 1954, such an event would probably not be bright enough to see through a telescope, but an impact would be - if the impact were on the side of Mars facing the Earth. If it were on the side facing away from Earth, then the incident would appear unexplained unless we had an orbiter at the right time and place.
Clark disputes the asteroid theory with a copy of a May 2001 Sky & Telescope article which cites him on pages 116 and 118. It shows that the flare he observed at the Edom Promontorium on Mars on July 24, 1954 was also seen at the same spot on Mars by Saheki 23 days earlier on July 1, 1954 and seen again there by Ichiro Tasaka on November 21, 1958. This would indicate a greater chance for a volcano there, but Tasaka also saw flares at the same night and at the same time in 1958 at Northern Hellas, which could be taken as evidence for an asteroid impact on Mars (Universal Times for the November 21, 1958 impacts at both Edom Promontorium and Northern Hellas were at 13:35 and 13:50). Either event, an asteroid impact or a huge volcanic eruption could account for the Martian dust storm.
Thomas A. Dobbins wrote in Sky & Telescope on March 4, 2004, that June 2001 observations support the idea that, “The flares came from sunlight glinting off patches of frost or ice on the Martian surface.” He states that “because the flashes occurred before Edom crossed the center of the planet's disk, the reflectors must have been tilted as much as 19° east-west; perhaps they rested on inclined surfaces on the ground, for example, the slopes of dunes. Intriguingly, the light-colored oval of Edom Promontorium corresponds to the large, flat crater Schiaparelli, and in May 2002 NASA's Mars Odyssey spacecraft found indications that this region is anomalously rich in water ice for a site near the Martian equator.” Of course, water can also reflect light, but the presence of liquid water can only occur over a sustained set of observations if the surface pressure is higher than NASA admits. Water would not stay tilted at the angle just indicated. Note: Mars is geologically dead, so I tend to doubt that volcanoes could cause the flares. Mostly likely asteroid impacts are the culprits.