gdal_translate -of GTiff -a_srs EPSG:4326 -a_ullr -180 90 180 -90 world.topo.bathy.200407.3x5400x2700.jpg world.topo.bathy.200407.3x5400x2700.tif

$ gdalinfo world.topo.bathy.200407.3x5400x2700.tif
Driver: GTiff/GeoTIFF
Files: world.topo.bathy.200407.3x5400x2700.tif
Size is 5400, 2700
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (-180.000000000000000,90.000000000000000)
Pixel Size = (0.066666666666667,-0.066666666666667)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (-180.0000000,  90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"N)
Lower Left  (-180.0000000, -90.0000000) (180d 0' 0.00"W, 90d 0' 0.00"S)
Upper Right ( 180.0000000,  90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"N)
Lower Right ( 180.0000000, -90.0000000) (180d 0' 0.00"E, 90d 0' 0.00"S)
Center      (   0.0000000,   0.0000000) (  0d 0' 0.01"E,  0d 0' 0.01"N)
Band 1 Block=5400x1 Type=Byte, ColorInterp=Red
Band 2 Block=5400x1 Type=Byte, ColorInterp=Green
Band 3 Block=5400x1 Type=Byte, ColorInterp=Blue

gdalwarp -s_srs EPSG:4326 -t_srs EPSG:3857 world.topo.bathy.200407.3x5400x2700.tif Marble_3857.tif

gdal2tiles.py --s_srs EPSG:3857 --zoom 0-3 -p 'raster' Marble_3857.tif