Astronomy Picture of the Day 3-12-02

NASA ^ | 3-12-02 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2002 March 12

Atete Corona on Venus
Credit: Magellan Spacecraft Team, USGS, NASA

Explanation: What could cause a huge cylindrical mountain to rise from the surface of Venus? Such features that occur on Venus are known as coronas. Pictured above in the foreground is 500-kilometer wide Atete Corona found in a region of Venus known as the Galindo. The image was created by combining multiple radar maps of the region to form a computer-generated three-dimensional perspective. The series of dark rectangles that crosses the image from top to bottom were created by the imaging procedure and are not real. The origin of massive coronas remains a mystery although speculation holds they result from some form of volcanism. Studying Venusian coronas help scientists better understand the inner structure of both Venus and Earth.

[petuniasevan]

Ignore the dashed lines on the image; they're imaging process artifacts.

Venus - one place I can't see manned exploration EVER occurring.

Mass (kg)............................................4.87 x 10^24
Diameter (km)........................................12104
Mean density (kg/m^3) ...............................5250
Escape velocity (m/sec)..............................10400

Average distance from Sun (AU).......................0.723
Rotation period (length of day in Earth days)........243.0 (retrograde)
Revolution period (length of year in Earth days).....224.7

Obliquity (tilt of axis degrees).....................178
Orbit inclination (degrees)..........................3.39
Orbit eccentricity (deviation from circular).........0.007

Mean surface temperature (K).........................726
Surface pressure.................................90 bars (Earth sea level = 1 bar)

Visual geometric albedo (reflectivity)...............0.59
Highest point on surface.............................Maxwell Montes (17 km above mean planetary radius)
Atmospheric components...............................96% carbon dioxide, 3% nitrogen, 0.003% water vapor
Surface materials....................................basaltic rock and altered materials

Compare that to Earth:

Mass (kg)............................................5.98 x 10^24
Diameter (km)........................................12756
Mean density (kg/m^3) ...............................5520
Escape velocity (m/sec)..............................11200

Average distance from Sun (AU).......................1
Rotation period (length of day in Earth hours).......23.93
Revolution period (length of year in Earth days).....365.26

Obliquity (tilt of axis in degrees)..................23.4
Orbit inclination (degrees)..........................0
Orbit eccentricity (deviation from circular).........0.017

Mean surface temperature (K).........................281
Maximum surface temperature (K)......................310
Minimum surface temperature (K)......................260

Visual geometric albedo (reflectivity)...............0.39
Highest point on surface.............................Mount Everest (over 8 km above sea-level)
Atmospheric components...............................78% nitrogen, 21% oxygen, 1% argon
Surface materials....................................basaltic and granitic rock and altered materials

[The Schnoid from Sheboygan]

The series of dark rectangles that crosses the image from top to bottom were created by the imaging procedure and are not real.

And here I was, thinking that the rectangles were zipper marks that resulted when they joined two photos together. ;-)

Seriously, though, the image is intriguing and it's always fun to see something from that website. Thanks for sharing.

[petuniasevan]

Haha. Actually, I was repeating the disclaimer for the image. Why?
Because there's ALWAYS someone who looks at the photo, sees something weird like that,
doesn't bother to READ THE TEXT, and asks, "What's that weird stuff?"

Glad you like the images. I'll certainly try to get them posted daily.

[fnord]

Ignore the dashed lines on the image; they're imaging process artifacts.

Yeah, sure. I can tell a Firestone FX-150-30 tire track when I see one. (j/k) :-)

[secret garden]

What a fabulous site! I've forwarded it to several teachers who can use it. Thanks for the post.

[snowfox]

Fasciating images. The surface of Venus is hot enough to melt lead, but I suspect that if some rare and valuable mineral is found there, we will find a way to extract it.

[snowfox]

Didn't Russia send a probe to the Venusian surface that got crushed by the pressure?

[petuniasevan]

Venera 9 Descent Craft

NSSDC ID:1975-050D

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Launch Date/Time: 1975-06-08 at 02:38:00 UTC
On-orbit dry mass: 2015 kg

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Description

On October 20, 1975, this spacecraft was separated from the Orbiter, and landing was made with the sun near zenith at 0513 UT on October 22. A system of circulating fluid was used to distribute the heat load. This system, plus precooling prior to entry, permitted operation of the spacecraft for 53 min after landing. During descent, heat dissipation and deceleration were accomplished sequentially by protective hemispheric shells, three parachutes, a disk-shaped drag brake, and a compressible, metal, doughnut-shaped, landing cushion. The landing was about 2,200 km from the Venera 10 landing site. Preliminary results indicated: (A) clouds 30-40 km thick with bases at 30-35 km altitude, (B) atmospheric constituents including HCl, HF, Br, and I, (C) surface pressure about 90 (earth) atmospheres, (D) surface temperature 485 deg C, (E) light levels comparable to those at earth midlatitudes on a cloudy summer day, and (F) successful TV photography showing shadows, no apparent dust in the air, and a variety of 30-40 cm rocks which were not eroded.

[petuniasevan]

Venera 10 Descent Craft

NSSDC ID:1975-054D

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Launch Date/Time: 1975-06-14 at 03:00:31 UTC
On-orbit dry mass: 2015 kg

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Description

On October 23, 1975, this spacecraft was separated from the Orbiter, and landing was made with the sun near zenith, at 0517 UT, on October 25. A system of circulating fluid was used to distribute the heat load. This system, plus precooling prior to entry, permitted operation of the spacecraft for 65 min after landing. During descent, heat dissipation and deceleration were accomplished sequentially by protective hemispheric shells, three parachutes, a disk-shaped drag brake, and a compressible, metal, doughnut-shaped, landing cushion. The landing was about 2,200 km distant from Venera 9. Preliminary results provided: (A) profile of altitude (km)/pressure (earth atmospheres)/temperature (deg C) of 42/3.3/158, 15/37/363, and 0/92/465, (B) successful TV photography showing large pancake rocks with lava or other weathered rocks in between, and (C) surface wind speed of 3.5 m/s.

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[petuniasevan]

Venera 13 Descent Craft

NSSDC ID:1981-106D

Other Name(s)

• Venera 13 Lander

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Launch Date/Time: 1981-10-30 at 06:04:00 UTC
On-orbit dry mass: 760 kg

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Description

Venera 13 and 14 were identical spacecraft built to take advantage of the 1981 Venus launch opportunity and launched 5 days apart. The Venera 13 mission consisted of a bus (81-106A) and an attached descent craft (81-106D). The Venera 13 descent craft/lander was a hermetically sealed pressure vessel, which contained most of the instrumentation and electronics, mounted on a ring-shaped landing platform and topped by an antenna. The design was similar to the earlier Venera 9-12 landers. It carried instruments to take chemical and isotopic measurements, monitor the spectrum of scattered sunlight, and record electric discharges during its descent phase through the Venusian atmosphere. The spacecraft utilized a camera system, an X-ray fluorescence spectrometer, a screw drill and surface sampler, a dynamic penetrometer, and a seismometer to conduct investigations on the surface.

After launch and a four month cruise to Venus, the descent vehicle separated from the bus and plunged into the Venus atmosphere on 1 March 1982. After entering the atmosphere a parachute was deployed. At an altitude of 47 km the parachute was released and simple airbraking was used the rest of the way to the surface. Venera 13 landed about 950 km northeast of Venera 14 at 7 deg 30 min S, 303 E, just east of the eastern extension of an elevated region known as Phoebe Regio. The area was composed of bedrock outcrops surrounded by dark, fine-grained soil. After landing an imaging panorama was started and a mechanical drilling arm reached to the surface and obtained a sample, which was deposited in a hermetically sealed chamber, maintained at 30 degrees C and a pressure of about .05 atmospheres. The composition of the sample determined by the X-ray flourescence spectrometer put it in the class of weakly differentiated melanocratic alkaline gabbroids. The lander survived for 127 minutes (the planned design life was 32 minutes) in an environment with a temperature of 457 degrees C and a pressure of 84 Earth atmospheres. The descent vehicle transmitted data to the bus, which acted as a data relay as it flew by Venus.

[petuniasevan]

In other words, these craft had to be built like a cross between a refrigerator and a fireproof safe, yet with a window to allow imaging.

Not only are we talking surface temps of around 900 degrees F, and atmospheric pressures of 90 times Earth sea level pressure, but also a strongly acidic environment.

Here's an image from one lander.

Venera 9 Lander image of the surface of Venus at about 32 S, 291 E. The Lander touched down at 5:13 UT with the sun near zenith on 22 October 1975 and operated for 53 minutes, allowing return of this single image. The white object at the bottom of the image is part of the lander. The distortion is caused by the Venera imaging system. Angular and partly weathered rocks, about 30 to 40 cm across, dominate the landscape, many partly buried in soil. The horizon is visible in the upper left and right corners. (Venera 9 Lander, surface image)

[snowfox]

84 Atmospheres of pressure and surrounded by an atmosphere of Hydrochloric acid and Iodine, two of the most corrosive substances that we know of. Truly a hellish place.