14. C. W. Hoganson et al., Photosyn. Res. 46, 177
(1995).
15. G. T. Babcock, in Photosynthesis: From Light to
Biosphere, P. Mathis, Ed. (Kluwer, Dordrecht, Neth-
erlands, 1995), vol. 2, pp. 209–215.
16. iiii, et al., Biochemistry 28, 9557 (1989).
17. G. W. Brudvig and R. H. Crabtree, Proc. Natl. Acad.
Sci. U.S.A. 83, 4586 (1986); J. B. Vincent and G.
Christou, Inorg. Chim. Acta 136, L41 (1987); V. L.
Pecoraro, in Manganese Redox Enzymes, V. L. Pec-
oraro, Ed. ( VCH, New York, 1992), pp. 197–231.
18. J. A. Gilbert et al., J. Am. Chem. Soc. 107, 3855
(1985); F. P. Rotzinger et al., ibid. 109, 6619 (1987);
Y. Naruta, M. Sasayama, T. Sasaki, Angew. Chem.
Int. Ed. 33, 1839 (1994).
19. J. Messinger, M. Badger, T. Wydrzynski, Proc.
Natl. Acad. Sci. U.S.A. 92, 3209 (1995); J. Mess-
inger, M. Hillier, M. Badger, T. Wydrzynski, in Pho-
tosynthesis: From Light to Biosphere, P. Mathis,
Ed. (Kluwer, Dordrecht, Netherlands, 1995), vol. 2,
pp. 283–286.
20. Kinetic inertness to substitution of the bridging oxo
atoms in Mn2(III,IV )(m-O)2 in superoxidized manga-
nese catalase has been suggested as the basis for
inactivity of this oxidation state; G. S. Waldo, S. Yu,
J. E. Penner-Hahn, J. Am. Chem. Soc. 114, 5869
(1992); S. Khangulov, M. Sivaraja, V. V. Barynin,
G. C. Dismukes, Biochemistry 32, 4912 (1993); M.
Shank, V. Barynin, G. C. Dismukes, ibid. 33, 15433
(1994).
21. J. Lind, X. Shen, T. E. Eriksen, G. Merenyi, J. Am.
Chem. Soc. 112, 479 (1990); J. A. Kerr, in Handbook
of Chemistry and Physics (Chemical Rubber, Cleve-
land, OH, ed. 77, 1996), pp. 9–51.
22. K. A. Gardner and J. M. Mayer, Science 269, 1849
(1995).
23. M. Baldwin and V. L. Pecoraro, J. Am. Chem. Soc.
118, 11325 (1996).
24. M. T. Caudle and V. L. Pecoraro, ibid. 119, 3415
(1997).
25. M. R. A. Blomberg et al., ibid., in press.
26. C. K. Ingold, Structure and Mechanism in Organic
Chemistry (Cornell Univ. Press, Ithaca, NY, ed. 2,
1969), pp. 457–463 and 681–686; A. Pross, Theo-
retical and Physical Principles of Organic Reactivity
( Wiley, New York, 1995).
27. H. Koike, B. Hanssum, Y. Inoue, G. Renger, Bio-
chim. Biophys. Acta 893, 524 (1987); G. Renger and
B. Hanssum, FEBS Lett. 299, 28 (1992).
28. N. Lydakis-Simantiris, C. W. Hoganson, D. F. Gha-
notakis, G. T. Babcock, in Photosynthesis: From
Light to Biosphere, P. Mathis, Ed. (Kluwer, Dor-
drecht, Netherlands, 1995), vol. 2, pp. 279–282;
N. Lydakis-Simantiris, D. F. Ghanotakis, G. T. Bab-
cock, Biochim. Biophys. Acta, in press.
29. O. Bo¨gershausen, M. Haumann, W. Junge, Ber.
Bunsenges. Phys. Chem. 100, 1987 (1996); M.
Karge, K.-D. Irrgang, G. Renger, Biochemistry 36,
8904 (1997).
30. M. Karge et al., FEBS Lett. 378, 140 (1996).
31. C. Tommos and G. T. Babcock, Acct. Chem. Res., in
press.
32. J. P. Dekker, H. J. Van Gorkom, J. Wensink, L.
Ouwehand, Biochim. Biophys. Acta 767, 1 (1984); J.
Lavergne, ibid. 1060, 175 (1991); M. Haumann, W.
Drevenstedt, M. Hundelt, W. Junge, ibid. 1273, 237
(1996); H. Kretschmann, E. Schlodder, H. T. Witt,
ibid. 1274, 1 (1996).
33. G. C. Dismukes and Y. Siderer, Proc. Natl. Acad.
Sci. U.S.A. 78, 274 (1981); A. Haddy, W. R. Dun-
ham, R. H. Sands, R. Aasa, Biochim. Biophys. Acta
1099, 25 (1992).
34. T. Ono et al., Science 258, 1335 (1992).
35. P. J. Riggs, C. F. Yocum, J. E. Penner-Hahn, R. Mei,
J. Am. Chem. Soc. 114, 10650 (1992).
36. T. A. Roelofs et al., Proc. Natl. Acad. Sci. U.S.A. 93,
3335 (1996).
37. Roeloffs et al. (36) argued against a Mn valence
change on S23S3, and Yachandra et al. (4) have
proposed that one-electron oxidation of the bridging
oxo group (or groups) occurs. However, a similar
bridging oxyl ligand formulation for intermediate X in
ribonucleotide reductase has been discarded re-
cently in favor of iron-centered oxidation in the binu-
clear cluster in that enzyme (58) and the free energy
necessary to generate an oxyl may be prohibitively
high (48). Accordingly, we disfavor an oxyl formula-
tion for S3.
38. P. J. Riggs-Gelasco, R. Mei, C. F. Yocum, J. E.
Penner-Hahn, J. Am. Chem. Soc. 118, 2387 (1996);
see also, J. Messinger, J. H. A. Nugent, M. C. W.
Evans, Biochemistry, in press.
39. J.-J. Girerd, in Photosynthesis: From Light to Bio-
sphere, P. Mathis, Ed. (Kluwer, Dordrecht, Nether-
lands, 1995), vol. 2, pp. 217–222.
40. I. Vass and S. Styring, Biochemistry 30, 830 (1991).
41. X.-S. Tang et al., Proc. Natl. Acad. Sci. U.S.A. 91,
704 (1994).
42. K. Lindberg, T. Va¨nngård, L.-E. Andre´asson, Photo-
syn. Res. 38, 401 (1993).
43. K. W. Kramarz and J. R. Norton, Prog. Inorg. Chem.
42, 1 (1994).
44. V. L. Pecoraro, Photochem. Photobiol. 48, 249
(1988).
45. D. W. Randall et al., J. Am. Chem. Soc. 117, 11780
(1995).
46. F. A. Cotton and G. Wilkinson, Advanced Inorganic
Chemistry ( Wiley, New York, ed. 5, 1988), p. 707;
N. N. Greenwood and A. Earnshaw, Chemistry of the
Elements (Pergamon, Oxford, 1984), p. 1228; R.
Manchandra, G. W. Brudvig, R. H. Crabtree, Coord.
Chem. Rev. 144, 1 (1995).
47. T. J. Collins, R. D. Powell, C. Slebodnick, E. S. Uffel-
man, J. Am. Chem. Soc. 112, 899 (1990); M. K.
Stern and J. T. Groves, in Manganese Redox En-
zymes, V. L. Pecoraro, Ed. ( VCH, New York, 1992),
pp. 233–259.
48. D. T. Sawyer, Oxygen Chemistry, (Oxford Univ.
Press, New York, 1991).
49. A. Chu, A. P. Nguyen, R. J. Debus, Biochemistry 34,
5859 (1995).
50. C. W. Hoganson and G. T. Babcock, in Metal Ions in
Biological Systems, vol. 30, Metalloenzymes Involv-
ing Amino Acid-Residue and Related Radicals, H.
Sigel and A. Sigel, Eds., (Dekker, New York, 1994),
pp. 77–107.
51. W. H. Saunders Jr. and A. F. Cockerill, Mechanisms
of Elimination Reactions ( Wiley, New York, 1973).
52. G. T. Babcock, R. E. Blankenship, K. Sauer, FEBS
Lett. 61, 286 (1976); M. R. Razeghifarad, C.
Klughammer, R. J. Pace, Biochemistry 36, 86
(1997).
53. A. Boussac, P. Se´tif, A. W. Rutherford, Biochemistry
31, 1224 (1992).
54. L. I. Krishtalik, Bioelectrochem. Bioenerg. 23, 249
(1990).
55. G. Tian, J. A. Berry, J. P. Klinman, Biochemistry 33,
226 (1994); J. P. Klinman, Chem. Rev. 96, 2541
(1996).
56. R. M. Wachter and B. P. Branchaud, J. Am. Chem.
Soc. 118, 2782 (1996).
57. C. F. Yocum, Biochim. Biophys. Acta 1059, 1 (1991);
H. Wincencjusz, H. J. van Gorkom, C. F. Yocum,
Biochemistry 36, 3663 (1997).
58. B. E. Sturgeon et al., J. Am. Chem. Soc. 118, 7551
(1996).
59. Supported by NIH grant GM-37300 and the USDA
Competitive Grants Office. We thank C. F. Yocum,
C. Tommos, K. Warncke, N. Lydakis-Simantiris
and M. Gardner for useful discussions.
26 October 1996; accepted 28 May 1997
RESEARCH ARTICLE
Global Sea Floor Topography
from Satellite Altimetry and
Ship Depth Soundings
Walter H. F. Smith* and David T. Sandwell
A digital bathymetric map of the oceans with a horizontal resolution of 1 to 12 kilometers
was derived by combining available depth soundings with high-resolution marine gravity
information from the Geosat and ERS-1 spacecraft. Previous global bathymetric maps
lacked features such as the 1600-kilometer-long Foundation Seamounts chain in the
South Pacific. This map shows relations among the distributions of depth, sea floor area,
and sea floor age that do not fit the predictions of deterministic models of subsidence
due to lithosphere cooling but may be explained by a stochastic model in which randomly
distributed reheating events warm the lithosphere and raise the ocean floor.
Knowledge of ocean floor topography data
is essential for understanding physical
oceanography, marine biology, chemistry,
and geology. Currents, tides, mixing, and
upwelling of nutrient-rich water are all in-
fluenced by topography. Seamounts may be
particularly important in mixing and tidal
dissipation (1), and deep water fisheries on
seamount flanks have become economically
significant (2). Seamounts, oceanic pla-
teaus, and other geologic structures associ-
ated with intraplate volcanism, plate
boundary processes, and the cooling and
subsidence of the oceanic lithosphere
should all be manifest in accurate bathy-
metric maps.
Conventional sea floor mapping is a te-
dious process. Ships have measured depth
with single-beam echo sounders since the
W. H. F. Smith is at the National Oceanic and Atmospher-
ic Administration, Code E/OC-2, 1315 East-West High-
way, Silver Spring, MD 20910–3282, USA.
D. T. Sandwell is at the Scripps Institution of Oceanogra-
phy, La Jolla, CA 92093, USA.
*To whom correspondence should be addressed. E-mail:
walter@amos.grdl.noaa.gov
SCIENCE
z
VOL. 277
z
26 SEPTEMBER 1997
z
www.sciencemag.org1956

60
°
N
30
°
N
30
°
S
60
°
S0°
0°
0°
30
°
E
60
°
E
90
°
E
12
0°
E
15
0°
E
18
0°
15
0°
W
12
0°
W
90
°
W
60
°
W
30
°
W
-
6
-
4
El
ev
at
io
n
(km
)
-
2
0
3
Fi
g.
1.
C
ol
or
sh
ad
ed
-r
el
ie
fi
m
ag
e
of
th
e
m
od
el
ed
to
po
gr
ap
hy
,i
llu
m
in
at
ed
fro
m
th
e
no
rth
w
es
t.
RESEARCH ARTICLE
www.sciencemag.org
z
SCIENCE
z
VOL. 277
z
26 SEPTEMBER 1997 1957