Sky & Telescope - October 2022 - 59

I
n many ways, robotic exploration of Mars has relegated
amateur astronomers to the status of telescopic tourists.
NASA's Mars Reconnaissance Orbiter has mapped
nearly the entire surface of the Red Planet at a resolution
of 6 meters (20 feet) or better. Five landers and six rovers
have sifted Martian soil and sniffed Martian air. In the
span of a single generation during the closing years of the
20th century, " the very character of the scientific questions
changed as the planets went from being astronomical objects
to geological objects, " notes William K. Hartmann of the
University of Arizona's Planetary Science Institute.
Yet a few mysteries from the era of earthbound planetary
exploration still linger. Prominent among them are Martian
" flares " - gleaming points of light that suddenly appear and
persist for a few seconds to several minutes before fading
from view.
Anomalous Observations
The earliest report of these rare phenomena dates from 1896,
when the British amateur John Milton Offord described a
" brilliant scintillating star-like point " appearing briefly in
Hellas, the vast ochre tract in the planet's southern hemisphere,
which we now know as an ancient impact basin.
During the following century, however, most flare sightings
would be reported by Japanese observers, who came to regard
spotting them as something of a specialty.
While observing Mars on the evening of June 4, 1937,
Sizuo Mayeda saw an intense, flickering point of light near
the morning limb at 55° north latitude. Far brighter than the
polar cap, it vanished after about 5 minutes.
Redux?
 Left: Tsuneo Saheki's sketches show the development of the December
8, 1951, flare at Tithonius Lacus. Right: The 1954 event at Edom
Promontorium drawn by Saheki was uncannily similar in both location
and appearance to the phenomenon recorded in 2001. Inset: Tsuneo
Saheki at the eyepiece of his venerable 8-inch f/10 Newtonian reflector.
On December 8, 1951, Tsuneo Saheki, one of Japan's leading
planetary observers, was examining Mars through an
8-inch reflector at 400× when he saw " . . . a sharp, bright,
glaring spot " suddenly appear at the eastern end of Tithonius
Lacus, a dusky feature in the Martian tropics. Decidedly
brighter than the polar cap, it disappeared after five minutes.
On July 1, 1954, Saheki saw a second flare, this time
at Edom Promontorium, a bright feature on the Martian
equator tucked into the nook formed by the junction of the
dusky features Sinus Sabaeus and Sinus Meridiani. Its slightly
elliptical outline corresponds to the ramparts of an ancient
impact crater 460 kilometers wide that now bears the name
Schiaparelli Basin. Lasting only a few seconds, this fleeting
event was less spectacular than the 1951 flare and wasn't as
bright as the polar cap.
Just 23 days later, Clark McClelland at Pittsburgh's Allegheny
Observatory witnessed a far more impressive flare at
Edom Promontorium. He reported that a white spot abruptly
appeared and rapidly grew brighter until it equaled a firstmagnitude
star before fading from view in under a minute.
Japanese observers reported another outbreak of flares
during the 1958 apparition of Mars. On November 7th, Sigeji
Tanabe saw a spot on the southwest edge of Tithonius Lacus
that grew as bright as the polar cap and faded from view after
four minutes. Four days later, Sanenobu Fukui witnessed a
spot as bright as the polar cap located between Tithonius
Lacus and nearby Solis Lacus that persisted for about five
minutes. On November 21st, the eminent Mars observer
Ichiro Tasaka saw flares at two widely separated places on
Mars, Edom Promontorium and the northern edge of Hellas.
They faded after a few minutes, only to brighten again 15
minutes later before vanishing.
Saheki wondered if the flares might be volcanic eruptions,
but University of Michigan astronomer Dean
McLaughlin pointed out that they were far too luminous
for that explanation to be correct. At the distance of Mars,
McLaughlin estimated that the fire fountains of the most
violent eruptions ever experienced on Earth would appear
thousands of times fainter than Saheki's 1951 flare and
would be invisible on the sunlit disc. " If these Martian
flares were volcanic, " he wrote, " they would indicate that
Martian volcanism is characterized by occasional great outbreaks
of incandescent gas a few kilometers in diameter and
sk yand tele scope .o r g * OCTOBER 2022 59
MARS: NASA / ESA / HUBBLE HERITAGE TEAM (STSCI / AURA), J. BELL (ASU), AND M. WOLFF
(SPACE SCIENCE INSTITUTE); SKETCHES AND INSET: TSUNEO SAHEKI (3)
http://skyandtelescope.org
Sky & Telescope - October 2022

Table of Contents for the Digital Edition of Sky & Telescope - October 2022
