Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (440 to 1000 nanometers) reveal three types of rock and four classes of soil. Upward-looking IMP images of the pre-dawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity ~ 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.

After Mars Pathfinder's landing on July 4, 1997, the Imager for Mars Pathfinder (IMP) [1] returned the first pictures of Mars from the surface since the Viking lander missions twenty-one years before. The panoramic views (Plate 1A) show a terrain littered with boulders stretching to a horizon graced by two hills (the "Twin Peaks"), the southern one conical with a vertical stripe, the northern one broader and banded with possible terraces. But stereoscopic views (Plate 1B) later revealed that the terrain between the lander and the "Twin Peaks" was a series of shallow gullies, some filled with fines material. This ridge and trough structure appears to be a remnant of the catastrophic floods that came through this area more than 2 billion years ago both from Tiu Vallis, southwest to northwest trend, and from Ares Vallis, south-southeast to north-northwest trend.

Here, along with the companion paper on the magnetic properties experiment [2], we present results on a range of topics from the geomorphology and mineralogy of the site to the atmospheric properties and astronomical observations. During the first 30 days of operation, the IMP returned 9,669 images from the surface of Mars; many of these are subframes taken of the Sun, various targets on the lander, or multi-spectral spots on selected rocks and soil. The large panoramas and their characteristics are listed in Table 1.

The Imager for Mars Pathfinder (IMP)­a stereo, multi-spectral camera­ is described in terms of its capabilities for studying the Martian environment. The cameraÕs two eyes, separated by 15.0 cm, provide the camera with range-finding ability. Each eye illuminates half of a single CCD detector with a FOV of 14.4x14.0° and has 12 selectable filters. The f/18 optics have a large depth of field and no focussing mechanism is required; a mechanical shutter is avoided by using the frame transfer capability of the 512 x 512 CCD. The resolving power of the camera, 0.98 mrad/pixel, is approximately the same as the Viking Lander cameras; however, the signal-to-noise ratio for IMP greatly exceeds Viking approaching 350. This feature along with the stable calibration of the filters between 440 and 1000 nm distinguishes IMP from Viking. Specially designed targets are positioned on the Lander; they provide information on the magnetic properties of wind-blown dust, measure the wind vectors, and provide radiometric standard reflectors for calibration. Also, eight low-transmission filters are included for imaging the Sun directly at multiple wavelengths giving IMP the ability to measure dust opacity and potentially the water vapor content. Several experiments beyond the requisite color panorama are described in detail: contour mapping of the local terrain, multi-spectral imaging of the surrounding rock and soil to study local mineralogy, viewing of three wind socks, measuring atmospheric opacity and water vapor content, and estimating the magnetic properties of wind blown dust. This paper is intended to serve as a guide to understanding the scientific integrity of the IMP data that will be returned from Mars starting on July 4, 1997.