June 2008 Sky from the Keeble Observatory
Phoenix has landed! For the first time since 1976, NASA and JPL have successfully
completed a powered landing on the Martian surface, this one about 70 degrees north
latitude, near but not on the north polar ice cap. (The last three successful Mars
landings used airbags rather than rockets to complete their touchdowns, finally
bouncing and rolling to a stop. Phoenix is too heavy for that scheme to have worked.)
All previous landings have been much closer to the Martian equator.
Initial reports (I’m writing this less than two days after the May 25 landing) indicate
that all is well. Project scientists are already thrilled with the images being
returned - including one of the descending lander on its parachute taken from orbit
by the Mars Reconnaissance Orbiter! Initially, they may not look that exciting –
certainly they’re less dramatic than some of the varied terrain studied by the rovers
Opportunity and Spirit for the last four years. However, the patterned terrain we’re
seeing is reminiscent of Earth’s arctic permafrost regions. On Earth, ice below
the surface expands and contracts with temperature changes, sometimes even partially
melting under the “midnight Sun” before refreezing. A similar phenomenon leads to
“frost heaves” on paved roads in many of our northern states. Project investigators
think that we are seeing the same thing happening on Mars – which may indicate the
presence of liquid water, even if only in small quantities and for short time intervals
during the Martian year.
Phoenix will dig several feet into the surface to find the ice and test it chemically
and with other instruments. We should be able to determine if the ice actually melts
at some time. Since all life as we know it (LAWKI) requires the presence of liquid
water, this would indicate the possibility that conditions may once have
been ripe for life on Mars. Early images returned from Phoenix show that the landing
thrusters actually cleared the surface soil to several inches depth, revealing a
tantalizing bright substrate which may well be the ice they hoped to find!
Phoenix is not expected to survive the Martian northern hemisphere winter, so the
primary mission timeline is to be completed in 90 days. Temperatures will drop to
the point where the solar panels are expected to be covered with frozen carbon dioxide
– “dry ice,” and the electronics will likely suffer irrecoverable damage. Yet, optimistic
mission controllers have programmed Phoenix with a “Lazarus mode” should the unexpected
happen and the power levels return after the long, dark winter.
Lunar phases for June: New Moon on the 3rd, at 3:23 pm; First
Quarter on the 10th, at 11:04 am; Full Moon on the 18th, at
1:30 pm; Last Quarter on the 26th, at 8:10 am.
Early risers will have few planetary targets for their efforts. Predawn skies find
only Jupiter has a reasonable viewing opportunity. Look for it low (about 25 degrees)
to the southwest. Venus is lost in the Sun’s glare, and will reach “superior conjunction”
on the 9th, when it will be on the opposite side of the Sun from our
vantage point. By month’s end, Mercury will return to the predawn skies, but will
be low to the east-northeast, only 15 degrees above the horizon before the sky brightens.
Evening viewers have more options. Mars and Saturn begin and end the month near
Regulus, in Leo. Mars will be in very close proximity by month’s end, with Saturn
within 5 degrees – this will make a nice binocular target. Jupiter rises east-southeast
about 3 hours after sunset, and moves across the southern sky. Venus will be low
(5 degrees) to the west-northwest by month’s end, probably lost in horizon clutter.
At midmonth, our overhead view finds the constellation Bootes (the Herdsman) at
zenith, with its brightest star Arcturus high to the south-southwest. To the west
we find the constellation Leo, with the above-mentioned trio of Mars, Saturn, and
Regulus. 5 degrees above and to the left of Saturn lies the elliptical galaxy known
as M105. (It’s the 105th entry in Charles Messier’s catalog of “fuzzy
things I don’t want to confuse with comets.”) Elliptical galaxies contain largely
an older population of stars, with little or no gas and dust, and virtually no ongoing
Below Arcturus, to the south-southwest the next bright star you’ll see is Spica
in the constellation Virgo. Starting again at zenith, sweeping binoculars slowly
toward the east you’ll encounter a globular cluster (M13, in Hercules) about 70
degrees above the horizon. Globular clusters like this one, orbital companions of
our own Galaxy, represent the oldest population of stars in the Milky Way’s halo.
They contain a gas-poor interstellar medium, virtually no star formation, and look
like nothing so much as miniature elliptical galaxies.
That bright star to the east-northeast is Vega, which is only 25.3 light years distant.
You may recall that it plays a key role in Carl Sagan’s novel Contact, and
the film starring Jodie Foster based on the book.
For your own monthly star chart, you can direct your web browser to
http://www.skymaps.com. You will find extensive descriptions of what's worth
looking for, and you can download and print a single copy for your personal use.